Math Concepts for Grade 9 Students

Convert 5 kilometers to meters.

• 50 meters

• 500 meters

• 5000 meters

• 50000 meters

Answer explanation

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

Express the number 0.00045 in scientific notation.

Answer explanation

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}.

Answer explanation

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.

What is the area of a triangle with a base of 8 cm and a height of 5 cm?

• 20 cm²

• 30 cm²

• 40 cm²

• 50 cm²

Answer explanation

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.

• 30°

• 45°

• 60°

• 90°

Answer explanation

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°.

Convert 2500 grams to kilograms.

• 0.25 kg

• 2.5 kg

• 25 kg

• 250 kg

Answer explanation

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

Express the number 7,200,000 in scientific notation.

Answer explanation

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.

Answer explanation

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.

• 21.98 cm

• 43.96 cm

• 50.24 cm

• 56.52 cm

Answer explanation

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.

• 30°

• 45°

• 60°

• 90°

Answer explanation

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°.