Question

The lockers at Smith High School are numbered 1-1000. Seth starts at the beginning and opens the even numbered lockers. Tacoda then starts at the beginning and opens all numbers that are multiples of 2. Lastly, Brady starts at the beginning and opens all numbers that are multiples of 5. Which is the first locker that Brady is supposed to open that is already open?

A) 10
B) 15
C) 30
D) 60

Answer 1

The answer is 10
I'm going to list the locker numbers by round:
Evens) 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, etc.
2's) 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, etc.
5's) 5, 10, 15, 20, 25, 30, 35, 40, etc.
The first number to repeat is 10, so that would be the first locker Brandy opens.
Hope this helped :)