Question

The average age of three boys is 15 years and their average in proportion 3:5:7, what is the age in years of the youngest boy?
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Answer 1

Answer:

let the age be 3x, 5x and 7x

average age is 15 then

3x+5x+7x=15

15x=15

x=15/15

x=1

the age of the youngest is 7x

since 7×1=7 year

Answer 2

Answer:

9 years

Step-by-step explanation:

average of three boys age = 15

therefore total age of three boys = 15×3= 45

therefore 3x + 5x + 7x = 45

15x = 45

x = 3

therefore three boys ages = 1) 3×3= 9 years

2) 5×3= 15 years

3) 7×3= 21 years

therefore youngest boys year is 9.