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Two numbers are in the ratio 5 : 7 and differ by 12. Their sum is:
A60
B84
C96
D72
Answer & Solution
Correct answer: D. 72
1. Call the numbers 5x and 7x so their ratio is fixed at 5 : 7.
2. Their difference is 7x - 5x = 2x.
3. Given 2x = 12, one part is x = 6.
4. The numbers are 30 and 42, so their sum is 72.
5. Equivalently the sum is 12x = 12 x 6 = 72.
_Source: NCERT Class 8 Maths, Ch 7 'Comparing Quantities', S7.1 Recalling Ratios and Percentages_
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