The answer is 300th caller. to find the answer you have to take the LCM of all three numbers of callers that are 15,25 and 100 so, lets take the LCM 5 15, 25, 100 ---------------------- 5 3, 5, 20 ----------------------- 3 3, 1, 4 ---------------------- 4 1, 1, 4 ----------------------- 1, 1, 1 Now ,multiply the numbers 5,5, 3 and 4. 5 x 5 x 3 x 4 = 25 x 12 = 300