Hard
The sum of the present ages of a father and his son is 50 years. Five years ago, the father was four times as old as the son. What is the present age of the son?
Explanation
Explanation
Step 1: Let the son's present age be s years. Then the father's present age = 50 − s.
Step 2: Five years ago: son = s − 5 and father = 50 − s − 5 = 45 − s.
Step 3: Given: father = 4 × son, so 45 − s = 4(s − 5).
Step 4: 45 − s = 4s − 20, so 65 = 5s and s = 13.
Step 5: Check: father now = 37. Five years ago: father 32, son 8, and 32 = 4 × 8 ✓.
Answer: 13 years.
PRO TIP
Re-check your working by substituting the answer back into the original question.