The average age of three boys is 15 yr. If the ratio of their ages is 3 : 5 : 7, what is the age of the oldest boy?
Correct Answer: Description for Correct answer:
Total age of all the three boys = 3 X 15 = 45 yr.
Ratio of ages = 3 : 5 : 7
Age of the oldest boy
= \( \large\frac{7}{3 + 5 + 7}\times 45 = \frac{7}{15} \times 45 = 21 yr \)
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