three babies A,B and C cry out at interval time. Baby A cries out at every 20 mins, while B cries out at every 30 mins and C cries out at every 40 mins. if they are observed at the same time, after what time will the three of them cry together? A. after 20 minutes B. after 30 minutes C. after 40 minutes D. after 120 minutes​
The answer will be D. After 120 minutes, because by looking at the three numbers, 20, 30, and 40, you have to find the common multiple for all three numbers, and in this case, 120 will fit all three numbers perfectly.
