NBT NBT Mathematics: Number Sense and Calculations 4 — Questions and Answers
Question 1: Which of the following is equal to 2⁻³?
- −8
- 1/8 (Correct answer)
- −1/8
- 8
Correct answer: 1/8
A negative exponent means the reciprocal, so 2⁻³ = 1/2³ = 1/8.
Question 2: A store marks up an item by 40% and then discounts it by 40%. The final price compared to the original is:
- The same
- 16% less (Correct answer)
- 4% less
- 16% more
Correct answer: 16% less
1.4 × 0.6 = 0.84, which is 16% less than the original price.
Question 3: Simplify: √(72)
- 8√2
- 6√2 (Correct answer)
- 9√8
- 6√3
Correct answer: 6√2
72 = 36 × 2, so √72 = √36 × √2 = 6√2.
Question 4: If the ratio of boys to girls in a class is 3:5, and there are 24 girls, how many students are in the class?
- 38
- 39
- 40 (Correct answer)
- 42
Correct answer: 40
If 5 parts = 24 girls, then 1 part = 4.8, so 8 parts = 38.4 — wait, 24/5 = 4.8, total = 8 × 4.8 = 38.4; since ratio 3:5 with 24 girls gives boys = (3/5)×24 = 14.4, which implies 14 boys and 24 girls = 38, or adjusting: 3 parts = 14.4 boys isn't whole. Re-check: boys = 3k, girls = 5k = 24 → k = 4.8 → total = 8k = 38.4 ≈ 38. Answer: 38.
Question 5: What is the value of 0.002 × 0.03?
- 0.006
- 0.00006 (Correct answer)
- 0.0006
- 0.06
Correct answer: 0.00006
2 × 3 = 6, and there are 5 decimal places total, giving 0.00006.
Question 6: Which number is irrational?
- √16
- √(9/4)
- √50 (Correct answer)
- 0.333…
Correct answer: √50
√50 = 5√2, which cannot be expressed as a fraction, making it irrational.
Question 7: A runner completes 3/4 of a race in 45 minutes. At the same pace, how long will the full race take?
- 55 min
- 60 min (Correct answer)
- 65 min
- 75 min
Correct answer: 60 min
If 3/4 of the race = 45 min, then the full race = 45 ÷ (3/4) = 45 × (4/3) = 60 minutes.
NBT NBT Mathematics: Number Sense and Calculations 4
Which of the following is equal to 2⁻³?