Question

In an apartment consisting of 108 floors, two lifts A and B starting from the ground floor, stop at every 3^rd and 5^th floors respectively. On which floors, will both of them stop together?

Answer 1

Multiples of 3 are 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 84, 87, 90, 93, 96, 99, 102, 105

Multiples of 5 are 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105

Common multiples of 3 and 5 are 15, 30, 45, 60, 75, 90 and 105

Both the lifts will stop at floors 15, 30, 45, 60, 75, 90 and 105