Question

(PLEASE HELP 100 POINTS)

Which pair of ratios form a proportion?

5 : 11 and 6 : 12

7 : 13 and 21 : 39

8 : 14 and 24 : 30

10 : 20 and 20 : 30

Answer 1

7/13 and 21/39

Cross multiply.

7 * 39 = 13 * 21

273 = 273

This is TRUE, so this forms a proportion.

Explanation:

Answer 2

5/11 and 6/12

• Cross multiply.
• 5 * 12 = 11 * 6
• 60 = 66
• This is UNTRUE, so this does not form a proportion.

7/13 and 21/39

• Cross multiply.
• 7 * 39 = 13 * 21
• 273 = 273
• This is TRUE, so this forms a proportion. Let's keep going to make sure that this is our answer.

8/14 and 24/30

• Cross multiply.
• 8 * 30 = 14 * 24
• 240 = 336
• This is UNTRUE, so this does not form a proportion.

10/20 and 20/30

• Cross multiply.
• 10 * 30 = 20 * 20
• 300 = 400
• This is UNTRUE, so this does not form a proportion.

Your answer is 7 : 13 and 21 : 39 are a pair of ratios that form a proportion.