A man is four times as old as his son. In five years he will be only three times as old as his son. What is the man's present age?

1 Answer
Daniel Tan
May 1, 2018

Man's present age : 40 years old.

Explanation:

Let man's age = #a#
Let son's age = #b#

Since a man is 4 times as old as his son, therefore
#a# = #4b#

In 5 years, he will only be 3 times as old as his son, therefore
#a+5 = 3(b+5)#

Apply substitution method :
#4b + 5 = 3b + 15#

#b = 10#

∴ #a = 40#

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