Question

when will 46 min and 69 min start at the same time again

Answer 1

You need to find the lowest common multiple of the two numbers by writing them as the product of their prime numbers so

46 = 2x23
69 = 3x23

Then you multiply these together, but as 23 occurs twice you only use one

23x2x3= 138
so they will start at the same time 138 minutes later (2 hours 18 mins)