Questions on Proportions Using Cross Products

 Questions on Proportions Using Cross Products

Multiple-choice questions on Proportions Using Cross Products, each with five alternatives (A–E). These are designed to help students practice solving proportions using the cross product method. The correct answers are listed at the end with full explanations.

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Proportions Using Cross Products – Multiple-Choice Questions

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1. Solve for $x$:
$\frac{2}{x} = \frac{4}{10}$
A) 3
B) 4
C) 5
D) 6
E) 8

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2. Find the missing value:
$\frac{3}{5} = \frac{x}{10}$
A) 4
B) 5
C) 6
D) 7
E) 8

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3. $\frac{6}{x} = \frac{9}{12}$
A) 6
B) 7
C) 8
D) 9
E) 10

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4. Solve:
$\frac{7}{14} = \frac{x}{28}$
A) 12
B) 10
C) 14
D) 16
E) 13

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5. Which value of $x$ makes this proportion true?
$\frac{x}{8} = \frac{15}{20}$
A) 6
B) 8
C) 10
D) 12
E) 14

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6. Find $x$:
$\frac{10}{x} = \frac{5}{4}$
A) 8
B) 6
C) 10
D) 7
E) 12

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7. Solve for $x$:
$\frac{x}{9} = \frac{12}{15}$
A) 6
B) 7
C) 8
D) 9
E) 10

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8. $\frac{8}{12} = \frac{2x}{36}$
A) 12
B) 18
C) 10
D) 14
E) 6

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9. Which value of $x$ satisfies:
$\frac{4}{x} = \frac{6}{9}$
A) 5
B) 6
C) 8
D) 7
E) 10

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10. Solve:
$\frac{9}{x} = \frac{3}{4}$
A) 12
B) 9
C) 6
D) 7
E) 8

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11. $\frac{x}{6} = \frac{12}{18}$
A) 3
B) 4
C) 5
D) 6
E) 7

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12. What value of $x$ solves:
$\frac{5}{x} = \frac{15}{21}$
A) 6
B) 7
C) 8
D) 9
E) 10

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13. Solve:
$\frac{3}{x} = \frac{6}{12}$
A) 5
B) 6
C) 4
D) 7
E) 3

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14. $\frac{x}{10} = \frac{9}{12}$
A) 6
B) 7.5
C) 8
D) 9
E) 10

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15. What value of $x$ makes this true?
$\frac{18}{x} = \frac{6}{5}$
A) 12
B) 14
C) 15
D) 16
E) 18

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16. Solve for $x$:
$\frac{x}{20} = \frac{8}{16}$
A) 8
B) 9
C) 10
D) 12
E) 6

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17. $\frac{7}{x} = \frac{14}{24}$
A) 10
B) 11
C) 12
D) 13
E) 14

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18. $\frac{x}{30} = \frac{5}{6}$
A) 20
B) 22
C) 24
D) 25
E) 26

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19. $\frac{2x}{8} = \frac{5}{10}$
A) 2
B) 2.5
C) 3
D) 3.5
E) 4

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20. Solve:
$\frac{x}{25} = \frac{9}{15}$
A) 12
B) 13
C) 14
D) 15
E) 16

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• Questions on Ratios as Decimals
• Questions on Identification and Writing of Equivalent Rates
• Questions on Comparison of Unit Rates

Answers with Explanations

1. C) 5
   Cross-multiply: $2 \cdot 10 = 20 = 4 \cdot x \Rightarrow x = 5$

2. C) 6
   $3 \cdot 10 = 30 = 5 \cdot x \Rightarrow x = 6$

3. C) 8
   $6 \cdot 12 = 72 = 9 \cdot x \Rightarrow x = 8$

4. C) 14
   $7 \cdot 28 = 196 = 14 \cdot x \Rightarrow x = 14$

5. A) 6
   $x \cdot 20 = 8 \cdot 15 \Rightarrow x = 120 / 20 = 6$
    

6. A) 8
   $10 \cdot 4 = 40 = 5 \cdot x \Rightarrow x = 8$

7. B) 7
   $x \cdot 15 = 9 \cdot 12 = 108 \Rightarrow x = 108 / 15 = 7.2$
   

8. A) 12
   Cross-multiply: $8 \cdot 36 = 2x \cdot 12 \Rightarrow 288 = 24x \Rightarrow x = 12$

9. B) 6
   $4 \cdot 9 = 36 = 6 \cdot x \Rightarrow x = 6$

10. A) 12
    $9 \cdot 4 = 36 = 3 \cdot x \Rightarrow x = 12$

11. B) 4
    $x = (12 \cdot 6)/18 = 72/18 = 4$

12. B) 7
    $5 \cdot 21 = 105 = 15 \cdot x \Rightarrow x = 7$

13. C) 6
    $3 \cdot 12 = 36 = 6 \cdot x \Rightarrow x = 6$

14. B) 7.5
    $x = 10 \cdot (9/12) = 7.5$

15. C) 15
    $18 \cdot 5 = 90 = 6 \cdot x \Rightarrow x = 15$

16. C) 10
    $x = (20 \cdot 8)/16 = 160/16 = 10$

17. C) 12
    $7 \cdot 24 = 168 = 14 \cdot x \Rightarrow x = 12$

18. C) 25
    $x = 30 \cdot (5/6) = 25$

19. B) 2.5
    $2x \cdot 10 = 8 \cdot 5 = 40 \Rightarrow x = 2.5$

20. D) 15
    $x = (9 \cdot 25)/15 = 225/15 = 15$

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Ronaldo Silva: Professor and Specialist in Science Teaching, from UFF/RJ, with more than 25 years of experience in teaching.