JAMB - Mathematics (1979 - No. 39)
A father is now three times as old as his son. Twelve years ago he was six times as old as his son. How old are the son and the father?
20 and 45
100 and 150
45 and 65
35 and 75
20 and 60
Vysvětlení
Son = x, Father = 3x, 12 yrs ago
son = x - 12, father = 3x - 12
3x - 12 = 6(x - 12)
3x - 12 = 6x - 72
3x = 60
x = 20
son = x - 12, father = 3x - 12
3x - 12 = 6(x - 12)
3x - 12 = 6x - 72
3x = 60
x = 20