Sarah’s age is one third of her fathers age. In 18 Years time her age will be half of her fathers age. How old is Sarah now

Question

find Sarah’s age and dads age to solve question

Answer 1

Sarah is 1/3 her father's age:

s = f/3

 

In 18 years she will be half her father's age:

s + 18 = (f+18)/2

2s + 36 = f + 18

2s = f - 18

 

Use substitution, replace s with f/3

 

2(f/3)= f - 18

2f/3 = f - 18

2f = 3f - 54

f = 54

 

s = f/3 = 18

 

Sarah is 18 years old.