a) 5 : 2
b) 7 : 3
c) 9 : 2
d) 13 : 4
Answer: b
Explanation: Let son’s age 10 years ago be x years,
Then man’s age 10 years ago = 3x years
Son’s present age = (x + 10) years
Man’s present age = (3x + 10) years
$$\eqalign{
& \left( {3x + 10} \right) + 10 = 2\left( {x + 10 + 10} \right) \cr
& 3x + 20 = 2\left( {x + 20} \right) \cr
& 3x + 20 = 2x + 40 \cr
& x = 20 \cr} $$
Ratio of present ages of man and the son
$$\eqalign{
& {\text{ = }}\frac{{3x + 10}}{{x + 10}} \cr
& = \frac{{3 \times 20 + 10}}{{20 + 10}} \cr
& = \frac{{70}}{{30}} \cr
& = 7:3 \cr} $$
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