Question

Sara is half her sisters age. In 20 years, she will be 3/4 her sister's age. How old is she?

Answer 1

40 years old

Explanation:

Let Sara be represented by P and her sister be represented by Q

`p = (q)/(2) \: \: equ1`

`p + 20 = (3q)/(4)`

From equ1, Q=2p

Substituting the value,

P+20= 3/4(2P)

`p + 20 = (3(2p))/(4)`

Cross multiplying,

4(P+20) = 6P

4P + 80 = 6P

Collect like terms

80 = 6P - 4P

80 = 2P

P = 80/2

P = 40

Therefore, Sara is 40 years old