Math Concepts for Grade 9 Students

To convert kilometers to meters, multiply by 1000. Therefore, 5 kilometers is 5 x 1000 = 5000 meters. The correct answer is 5000 meters.

To express 0.00045 in scientific notation, move the decimal point 4 places to the right, giving 4.5. This corresponds to multiplying by 10 raised to the power of -4, so the correct answer is 4.5 \times 10^{-4}.

To solve for x in the equation 2x + 3 = 11, first subtract 3 from both sides to get 2x = 8. Then, divide both sides by 2 to find x = 4. Thus, the correct answer is x = 4.

The area of a triangle is calculated using the formula: Area = 1/2 × base × height. Here, Area = 1/2 × 8 cm × 5 cm = 20 cm². Therefore, the correct answer is 20 cm².

Since \( \sin(30°) = \frac{1}{2} \), the value of \( \theta \) that satisfies \( \sin(\theta) = \frac{1}{2} \) is 30°. Therefore, the correct answer is 30°.

To convert grams to kilograms, divide by 1000. Thus, 2500 grams ÷ 1000 = 2.5 kg. Therefore, the correct answer is 2.5 kg.

To express 7,200,000 in scientific notation, we write it as 7.2 multiplied by 10 raised to the power of 6, since the decimal moves 6 places to the left. Thus, the correct answer is 7.2 \times 10^6.

To solve for y in the equation 3y - 4 = 11, first add 4 to both sides to get 3y = 15. Then, divide both sides by 3 to find y = 5. Thus, the correct answer is y = 5.

To find the circumference of a circle, use the formula C = 2πr. Here, r = 7 cm. Thus, C = 2 × 3.14 × 7 = 43.96 cm. Therefore, the correct answer is 43.96 cm.

The cosine of 60° is ½, and the cosine of 30° is ¾. Since ¾ corresponds to à, the correct angle for θ where à = à is 60°. Thus, θ = 60°.