An electronic calculator is a small, portable electronic device used to perform both arithmetic operations and complex mathematical operations.

The first solid electronic calculator was created in the 1960s, building on the extensive history of tools such as the abacus (developed around 2000 BC), and the mechanical calculator (developed in the 17^th century AD). It was developed in parallel with the analog computers of the day.

In addition to general purpose of calculators, there are those designed for specific markets, for example, there are scientific calculators which include trigonometric and statistical calculations. Some calculators even have the ability to do computer algebra. Graphing calculators can be used to graph functions defined on the real line, or higher dimensional Euclidean space.

When does the mechanical calculator developed?

An electronic calculator is a small, portable electronic device used to perform both arithmetic operations and complex mathematical operations.

The first solid electronic calculator was created in the 1960s, building on the extensive history of tools such as the abacus (developed around 2000 BC), and the mechanical calculator (developed in the 17^th century AD). It was developed in parallel with the analog computers of the day.

In addition to general purpose of calculators, there are those designed for specific markets, for example, there are scientific calculators which include trigonometric and statistical calculations. Some calculators even have the ability to do computer algebra. Graphing calculators can be used to graph functions defined on the real line, or higher dimensional Euclidean space.

What is the meaning of “extensive” in the second paragraph?

An electronic calculator is a small, portable electronic device used to perform both arithmetic operations and complex mathematical operations.

The first solid electronic calculator was created in the 1960 s, building on the extensive history of tools such as the abacus (developed around 2000 BC), and the mechanical calculator (developed in the 17^th century AD). It was developed in parallel with the analog computers of the day.

In addition to general purpose of calculators, there are those designed for specific markets, for example, there are scientific calculators which include trigonometric and statistical calculations. Some calculators even have the ability to do computer algebra. Graphing calculators can be used to graph functions defined on the real line, or higher dimensional Euclidean space.

It was developed in parallel with the analog computers of the day. The underlined word refers to ...

An electronic calculator is a small, portable electronic device used to perform both arithmetic operations and complex mathematical operations.

The first solid electronic calculator was created in the 1960s, building on the extensive history of tools such as the abacus (developed around 2000 BC), and the mechanical calculator (developed in the 17^th century AD). It was developed in parallel with the analog computers of the day.

In addition to general purpose of calculators, there are those designed for specific markets, for example, there are scientific calculators which include trigonometric and statistical calculations. Some calculators even have the ability to do computer algebra. Graphing calculators can be used to graph functions defined on the real line, or higher dimensional Euclidean space.

What is the main idea of paragraph 3?

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

What is the purpose of the text above?

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

A public place where we can have free access to the internet is …

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

A laptop has become very popular because …

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

“ …a laptop allows us….” (paragraph 1 line 1)

The underlined word has the opposite meaning with …

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

From the text we know that ….

A laptop is a kind of computer unit which has the same function as a PC (Personal Computer), but it’s smaller, lighter and of different sizes. Nowadays, most people choose laptops for several reasons.

A laptop is a portable device. This portability is very helpful for our work, study and other activities. We do not need complicated cable installations to activate a laptop. With a laptop, we can do our work anytime and anywhere.

Moreover, a laptop allows us to access the internet in public places which provide free access called hot spot areas. Some people like to use this facility to carry out their tasks.

Finally, a laptop consumes energy more efficiently than a PC does. This device uses a rechargeable battery as a source of electric energy. So, if we prefer using a laptop, it means that we support the government program to save energy. That’s why a laptop has become very popular recently.

From the text we know that ….

Glasses—also called eyeglasses (formal), spectacles, or specs (informal)—are frames bearing lenses worn in front of the eyes, normally for vision correction or eye protection. Safety glasses are kind of eye protection against flying debris or against visible and near visible light or radiation. Sunglasses allow better vision in bright daylight, and may protect against damage from high levels of ultraviolet light. Other types of glasses may be used for viewing visual information (such as stereoscope) or simply just for aesthetic or fashion values.

Historical types of glasses include the pincers, monocle, lorgnette, and scissors or scissors-glasses.

Modern glasses are typically supported by pads on the bridge of the nose and by temple arms (sides) placed over the ears. CR-39 lenses are the most common plastic lenses due to their low weight, high scratch resistance, low dispersion, and low transparency to ultraviolet and infrared radiation. Polycarbonate and Trivex lenses are the lightest and most shatter-resistant, making them the best for impact protection.

An unpopular aspect of glasses is their inconvenience. Even through the creation of light frames such as those made of titanium, very flexible frames and new lens materials and optical coatings, glasses can still cause problems during rigorous sport, Visibility can be significantly reduced by becoming greasy, trapping vapour when eating hot food, swimming, walking in rain or rapid temperature changes (such as walking into a warm building from cold temperature outside). Scraping, fracturing, or breakage of the lenses require time—consuming and costly professional repair, though modern plastic lenses are almost indestructible and very scratch—resistant.

What is one good point of CR – 39 lenses?

Glasses—also called eyeglasses (formal), spectacles, or specs (informal)—are frames bearing lenses worn in front of the eyes, normally for vision correction or eye protection. Safety glasses are kind of eye protection against flying debris or against visible and near visible light or radiation. Sunglasses allow better vision in bright daylight, and may protect against damage from high levels of ultraviolet light. Other types of glasses may be used for viewing visual information (such as stereoscope) or simply just for aesthetic or fashion values.

Historical types of glasses include the pincers, monocle, lorgnette, and scissors or scissors-glasses.

Modern glasses are typically supported by pads on the bridge of the nose and by temple arms (sides) placed over the ears. CR-39 lenses are the most common plastic lenses due to their low weight, high scratch resistance, low dispersion, and low transparency to ultraviolet and infrared radiation. Polycarbonate and Trivex lenses are the lightest and most shatter-resistant, making them the best for impact protection.

An unpopular aspect of glasses is their inconvenience. Even through the creation of light frames such as those made of titanium, very flexible frames and new lens materials and optical coatings, glasses can still cause problems during rigorous sport, Visibility can be significantly reduced by becoming greasy, trapping vapour when eating hot food, swimming, walking in rain or rapid temperature changes (such as walking into a warm building from cold temperature outside). Scraping, fracturing, or breakage of the lenses require time—consuming and costly professional repair, though modern plastic lenses are almost indestructible and very scratch—resistant.

Why do people like frames made of titanium?

Glasses—also called eyeglasses (formal), spectacles, or specs (informal)—are frames bearing lenses worn in front of the eyes, normally for vision correction or eye protection. Safety glasses are kind of eye protection against flying debris or against visible and near visible light or radiation. Sunglasses allow better vision in bright daylight, and may protect against damage from high levels of ultraviolet light. Other types of glasses may be used for viewing visual information (such as stereoscope) or simply just for aesthetic or fashion values.

Historical types of glasses include the pincers, monocle, lorgnette, and scissors or scissors-glasses.

Modern glasses are typically supported by pads on the bridge of the nose and by temple arms (sides) placed over the ears. CR-39 lenses are the most common plastic lenses due to their low weight, high scratch resistance, low dispersion, and low transparency to ultraviolet and infrared radiation. Polycarbonate and Trivex lenses are the lightest and most shatter-resistant, making them the best for impact protection.

An unpopular aspect of glasses is their inconvenience. Even through the creation of light frames such as those made of titanium, very flexible frames and new lens materials and optical coatings, glasses can still cause problems during rigorous sport, Visibility can be significantly reduced by becoming greasy, trapping vapour when eating hot food, swimming, walking in rain or rapid temperature changes (such as walking into a warm building from cold temperature outside). Scraping, fracturing, or breakage of the lenses require time—consuming and costly professional repair, though modern plastic lenses are almost indestructible and very scratch—resistant.

At the workshop or repair shops, the mechanic puts on glasses to....

An eclipse is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth.

Eclipses may occur when the Earth and Moon are aligned with the Sun, and the shadow of one body cast by the Sun falls on the other. So at New Moon (or rather Dark Moon), when the Moon is in conjunction with the Sun, the Moon may pass in front of the Sun as seen from a narrow region on the surface of the Earth and cause a solar eclipse. At Full Moon, when the Moon is in opposition to the Sun, the Moon may pass through the shadow of the Earth, and a lunar eclipse is visible from the night half of the Earth.

An eclipse does not happen at every New or Full Moon, because the plane of the orbit of the Moon around the Earth is tilted with respect to the plane of the orbit of the Earth around the Sun, so as seen from the Earth, when the Moon is nearest to the Sun (New Moon) or at largest distance (Full Moon), the three bodies usually are not exactly on the same line.

When does lunar eclipse happen?

An eclipse is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth.

Eclipses may occur when the Earth and Moon are aligned with the Sun, and the shadow of one body cast by the Sun falls on the other. So at New Moon (or rather Dark Moon), when the Moon is in conjunction with the Sun, the Moon may pass in front of the Sun as seen from a narrow region on the surface of the Earth and cause a solar eclipse. At Full Moon, when the Moon is in opposition to the Sun, the Moon may pass through the shadow of the Earth, and a lunar eclipse is visible from the night half of the Earth.

An eclipse does not happen at every New or Full Moon, because the plane of the orbit of the Moon around the Earth is tilted with respect to the plane of the orbit of the Earth around the Sun, so as seen from the Earth, when the Moon is nearest to the Sun (New Moon) or at largest distance (Full Moon), the three bodies usually are not exactly on the same line.

What is the main idea of the third paagraph?

An eclipse is an astronomical event that occurs when one celestial object moves into the shadow of another. The term is most often used to describe either a solar eclipse, when the Moon's shadow crosses the Earth's surface, or a lunar eclipse, when the Moon moves into the shadow of Earth.

Eclipses may occur when the Earth and Moon are aligned with the Sun, and the shadow of one body cast by the Sun falls on the other. So at New Moon (or rather Dark Moon), when the Moon is in conjunction with the Sun, the Moon may pass in front of the Sun as seen from a narrow region on the surface of the Earth and cause a solar eclipse. At Full Moon, when the Moon is in opposition to the Sun, the Moon may pass through the shadow of the Earth, and a lunar eclipse is visible from the night half of the Earth.

An eclipse does not happen at every New or Full Moon, because the plane of the orbit of the Moon around the Earth is tilted with respect to the plane of the orbit of the Earth around the Sun, so as seen from the Earth, when the Moon is nearest to the Sun (New Moon) or at largest distance (Full Moon), the three bodies usually are not exactly on the same line.

What will happen if the Moon's shadow crosses the Earth's surface? There will be ….