Question

Genevieve forgot the last two digits of her four-digit locker code: 21?? If the number is divisible hy 5,6, and 7, what is Genevieve's locker code?

Answer 1

If a number is divisible by 5, 6, and 7, 

it's divisible by 5 x 6 x 7 = 210, the least 

common multiple of the numbers. So her number 

is a multiple of 210. The only 4-digit multiple 

is 210 that starts 210 _ is 2100, so that's her number.