Which set of four numbers is NOT in proportion when taken in the order given?

Class 6Ratio and ProportionRatio and Proportion

Step-by-Step Solution

Apply the cross product to each set:

4 \times 35 = 140 = 10 \times 14

;

9 \times 10 = 90 = 6 \times 15

;

3 \times 32 = 96 = 8 \times 12

. But

6 \times 21 = 126

while

8 \times 15 = 120

, and 126 is not 120, so 6, 8, 15, 21 are not in proportion.

Answer: C) 6, 8, 15, 21

If a :

b = c : d

, the four numbers are in proportion. The classic check: the **product of the extremes**

(a \times d)

equals the **product of the means**

(b \times c)

. Example: are 4 : 6 and 6 : 9 in proportion? Cross-multiply:

4 \times 9 = 36, 6 \times 6 = 36

. Equal → yes, in proportion.

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