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16. Present age of father is 42 years and that of his son is 14 years. Find the ratio of
(a) Present age of father to the present age of son.
(b) Age of the father to the age of son, when son was 12 years old.
(c) Age of father after 10 years to the age of son after 10 years.
(d) Age of father to the age of son when father was 30 years old.
SOLUTION:
a) Father’s present age: Son’s present age = 42:14 = 6:2 = 3:1
b) If son’s age = 12 years old
Then father’s age = 42 -2 = 40 years
Therefore the required ratio = 40:12 = 10:3
c) Age of father after 10 years: age of son after 10 years
= ( 42 + 10 ):( 14 + 10 ) = 52 : 24 = 13 : 6
d) When father’s age = 30 years
Son’s age = 14 – 12 = 2 years
Therefore the required ratio = 30 : 2 = 15 : 1

4) FINDING THE RATIO (NCERT, Ex-12.1, pg-251)
Case -1: when the units are same
Q.6 (d) 30 minutes to 45 minutes

30 minutes : 45 minutes = = = = 2:3

Case -2: when the units are different
7. Find the ratio of the following:
(a) 30 minutes to 1.5 hours
1 hr = 60 minutes
1.5 hours = 1.5 x 60 = 90 minutes

30 minutes : 1.5 hours = 30 : 90 = = = = 1:3

Video Link:
https://www.khanacademy.org/math/pre-algebra/pre-algebra-ratios-rates/pre-algebra-ratios-
intro/v/equivalent-ratios
https://www.khanacademy.org/math/pre-algebra/pre-algebra-ratios-rates/pre-algebra-ratios-
intro/v/ratios-intro