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Five Years Ago a Man Was Seven Times as Old as His Son. Five Years Hence, the Father Will Be Three Times as Old as His Son. Find Their Present Ages. - Mathematics

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Question

Five years ago a man was seven times as old as his son. Five years hence, the father will be three times as old as his son. Find their present ages.

Sum

Solution

Five years ago: 
Let the age of the son be x years . 
Therefore, the age of the father will be 7x years . 
∴ Present age of the son = (x + 5) years
 Present age of the father = (7x + 5) years
After five years: 
Age of the son = (x + 5 + 5) = (x + 10) years
Age of the father = (7x + 5 + 5) = (7x + 10) years
According to the question, 
7x + 10 = 3(x + 10)
or 7x - 3x = 30 - 10
or 4x = 20
or x = 5
∴ Present age of the son = (5 + 5) = 10 years . \]
Present age of the father =\[ (7 \times 5 + 5) = 40\text{ years }.\]

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Chapter 9: Linear Equation in One Variable - Exercise 9.4 [Page 30]

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RD Sharma Mathematics [English] Class 8
Chapter 9 Linear Equation in One Variable
Exercise 9.4 | Q 13 | Page 30

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