Question

Traffic lights at three different road crossing change after 48 sec,72sec and 108 sec respectively. At what time will they change together again if they change simultaneously at 7 A.M.? (with full statement )

Answer 1

the common multiple between three nos. is 3456
48x72=3456
72x48=3456
108x32=3456
hence they will together after 3456seconds that is 57mins and 36seconds later. If it is 7.am then it will change at 7hours 57mins and36seconds