Proportions and Percent Problems Flashcard

Front

What is a proportion?

Back

A proportion is an equation that states that two ratios are equal.

Front

How do you calculate a percentage of a number?

Back

To calculate a percentage of a number, multiply the number by the percentage (in decimal form). For example, to find 20% of 50, calculate 50 x 0.20 = 10.

Front

What is the formula to find the original price after a discount?

Back

Original Price = Sale Price / (1 - Discount Rate). For example, if a jacket costs $75 after a 25% discount, the original price is $75 / (1 - 0.25) = $100.

Front

How do you find the discount amount?

Back

Discount Amount = Original Price x Discount Rate. For example, for a $200 item with a 15% discount, the discount amount is $200 x 0.15 = $30.

Front

What is the formula for average speed?

Back

Average Speed = Total Distance / Total Time. For example, if a car travels 180 miles in 3 hours, the average speed is 180 miles / 3 hours = 60 mph.

Front

How do you calculate the new price after a discount?

Back

New Price = Original Price - Discount Amount. For example, if an item costs $200 and has a $30 discount, the new price is $200 - $30 = $170.

Front

What does it mean for a population to double?

Back

When a population doubles, it means that the number of individuals becomes twice as large as it was before.

Front

If a bacteria population doubles every 3 hours, how many times does it double in 9 hours?

Back

It doubles 3 times in 9 hours (9 hours / 3 hours per doubling = 3 doublings).

Front

What is the relationship between ratios and proportions?

Back

Ratios compare two quantities, while proportions state that two ratios are equal.

Front

How do you convert a fraction to a percentage?

Back

To convert a fraction to a percentage, divide the numerator by the denominator and multiply by 100. For example, 1/4 = (1 ÷ 4) x 100 = 25%.