Find the number that must be added to both terms of the ratio 13:25 to make it equal to 7:10.

B11

C15 ✓ Correct

D13

Correct answer: (C) 15

Explanation

The number to add is 15.

Require (13+x)/(25+x) = 7/10.

Cross-multiply: 10(13+x) = 7(25+x).

130 + 10x = 175 + 7x, so 3x = 45.

x = 15.

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