Five years ago, mother was thrice as old as daughter. Mother is now $40$. Daughter's present age is

Five years ago, mother was thrice as old as daughter. Mother is now $40$. Daughter's present age is
  1. $\dfrac{50}{3}$
  2. $15$
  3. $20$
  4. $10$

Solution

5 yrs ago: $35 = 3(d-5) \Rightarrow 3d = 50 \Rightarrow d = \dfrac{50}{3}$.

Asked in: IMO

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