Question

Each bus takes about 15 minutes to refill and there are two buses to be refilled. So they stop there for about __________ minutes, which means they are late by about _________ minutes.

Answer 1

Time taken by 1 bus to refill = 15 minutes
Time taken by 2 buses to refill = 2$\times$15 = 30 minutes
So, the two buses take 30 minutes to refill.
They are late by about 30 minutes.
Each bus takes about 15 minutes to refill and there are two buses to be refilled. So, they stop there for about 30 minutes, which means they are late by about 30 minutes.