Answer:
840 minutes
Step-by-step explanation:
We solve this question using the LCM Method
Find and list multiples of each number of minutes which is given in the quest as 140, 210 and 280 minutes until the first common multiple is found. This is the lowest common multiple.
Multiples of 140:
140, 280, 420, 560, 700, 840, 980, 1120
Multiples of 210:
210, 420, 630, 840, 1050, 1260
Multiples of 280:
280, 560, 840, 1120, 1400
Therefore,
LCM(140, 210, 280) = 840
Therefore, they would have to wait after their first break together to get together again after 840 minutes
