Real Numbers

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ACT Math › Real Numbers

Questions 1 - 10
1

What is the absolute value of $-\frac{7}{3}$?

$-\frac{7}{3}$

$\frac{3}{7}$

$7$

$\frac{7}{3}$

Explanation

The absolute value of a number is its distance from zero on the number line, always positive or zero. The absolute value of $-\frac{7}{3}$ is the distance from $-\frac{7}{3}$ to 0, which is $\frac{7}{3}$ units. Therefore, $|-\frac{7}{3}| = \frac{7}{3}$.

2

Which number is greatest? $-0.5$, $0.1$, $-0.1$, $0.05$

$-0.1$

$0.05$

$-0.5$

$0.1$

Explanation

We need to identify the greatest among -0.5, 0.1, -0.1, and 0.05. On the number line, positive numbers are greater than negative numbers, and among positive numbers, larger values are to the right. Comparing the positive values: 0.1 > 0.05, and both are greater than the negative values -0.5 and -0.1. Therefore, 0.1 is the greatest.

3

What is the absolute value of $-\frac{9}{4}$?

$\frac{4}{9}$

$\frac{9}{4}$

$-\frac{9}{4}$

$9$

Explanation

The absolute value of a number is its distance from zero on the number line, which is always positive or zero. The absolute value of $-\frac{9}{4}$ is the distance from $-\frac{9}{4}$ to 0, which is $\frac{9}{4}$ units. Therefore, $ \left| -\frac{9}{4} \right| = \frac{9}{4} $.

4

Which number is smallest? $-2$, $-\frac{3}{4}$, $0.5$, $1$

$-\frac{3}{4}$

$-2$

$1$

$0.5$

Explanation

We need to identify the smallest among -2, -3/4, 0.5, and 1. Convert to decimals: -2 = -2, -3/4 = -0.75, 0.5 = 0.5, 1 = 1. On the number line, negative numbers are to the left of positive numbers, and among negative numbers, the one with greater absolute value is smaller. Since |-2| = 2 > |-0.75| = 0.75, -2 is smaller than -0.75.

5

Which expression represents a real number? $\sqrt{-1}$, $\ln(-1)$, $4^{0.5}$, $\frac{1}{0}$

$4^{0.5}$

$\ln(-1)$

$\sqrt{-1}$

$\frac{1}{0}$

Explanation

We need to identify which expression represents a real number. √(-1) is undefined in real numbers (square root of negative), ln(-1) is undefined (logarithm of negative), $4^0$.5 = √4 = 2 is a positive real number, and 1/0 is undefined (division by zero). Only $4^0$.5 represents a real number.

6

Which of the following lists the numbers $3.14$, $\pi$, and $\frac{22}{7}$ in order from least to greatest? (Note: $\pi \approx 3.14159...$)

$\dfrac{22}{7} < \pi < 3.14$

$3.14 < \dfrac{22}{7} < \pi$

$3.14 < \pi < \dfrac{22}{7}$

$\pi < 3.14 < \dfrac{22}{7}$

Explanation

This is an ordering of real numbers question testing number sense with irrational numbers. Choice B (3.14 < π < 22/7) is correct — converting to decimals: 3.14 = 3.1400..., π ≈ 3.14159..., 22/7 ≈ 3.14286. The correct order from least to greatest is: 3.14 < π < 22/7. Choice A (3.14 < 22/7 < π) places 3.14 correctly but swaps π and 22/7 — a very common error since 22/7 is often introduced as a shorthand for π, but it is actually slightly larger than π. Choice C (π < 3.14 < 22/7) incorrectly places π below 3.14, reversing their actual relationship — π ≈ 3.14159, which is greater than 3.14. Choice D (22/7 < π < 3.14) inverts the entire order, placing 22/7 as the smallest when it is actually the largest. Pro tip: Convert all three to decimals before comparing: 22 ÷ 7 ≈ 3.142857. This removes any ambiguity. Remember: 22/7 is a common approximation for π, but it overestimates π by about 0.001.

7

What is the approximate value of $\sqrt{3}$?

$1.7$

$1.83$

$1.8$

$1.73$

Explanation

To approximate $\sqrt{3}$, we find perfect squares near 3. Since $1^2 = 1$ and $2^2 = 4$, $\sqrt{3}$ is between 1 and 2. More precisely, $1.7^2 = 2.89$ and $1.8^2 = 3.24$, so $\sqrt{3}$ is between 1.7 and 1.8. Calculating: $1.73^2 = 2.9929 \approx 3$, so $\sqrt{3} \approx 1.73$.

8

Which number is greatest? $-5$, $-2$, $0$, $3$.

$-5$

$0$

$3$

$-2$

Explanation

We need to identify which number is greatest among -5, -2, 0, and 3. On the number line from left to right: -5 < -2 < 0 < 3. The rightmost position represents the greatest value. Therefore, 3 is the greatest number. Choice A incorrectly thought -5 was greatest, confusing the magnitude of negative numbers with their actual value.

9

Which represents a rational number? $\sqrt{11}$, $0.75$, $\pi$, $e$

$\sqrt{11}$

$\pi$

$0.75$

$e$

Explanation

A rational number can be expressed as a fraction p/q where p and q are integers and q ≠ 0. √11 is irrational, 0.75 = 75/100 = 3/4 is rational (terminating decimal), π is irrational, and e is irrational. The decimal 0.75 terminates, making it rational.

10

Which number is greatest? $-3.5$, $-2.75$, $-4$, $-1.25$.

$-4$

$-3.5$

$-1.25$

$-2.75$

Explanation

We need to identify which number is greatest among -3.5, -2.75, -4, and -1.25. All numbers are negative, so the one closest to zero is greatest. On the number line from left to right: -4 < -3.5 < -2.75 < -1.25. The rightmost position represents the greatest value. Therefore, -1.25 is the greatest number. Choice A incorrectly selected -3.5, not understanding that among negative numbers, the one with smallest magnitude is greatest.

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