The bus stop is the starting point of No.1 bus and No.5 bus. After the first bus leaves at 6 a.m., No.1 bus leaves every 15 minutes No.5 bus leaves every 12 minutes. At least how long does it take for two buses to leave at the same time?

The bus stop is the starting point of No.1 bus and No.5 bus. After the first bus leaves at 6 a.m., No.1 bus leaves every 15 minutes No.5 bus leaves every 12 minutes. At least how long does it take for two buses to leave at the same time?

First, find out the least common multiple of No.1 vehicle and No.5 vehicle
[15,12] = 3 × 4 × 5 = 60 (min) = 1 (H)
A: after at least one hour, the two buses will start at the same time

A car delivers goods to the mountain area, 42 kilometers per hour, 67 hours to arrive. It only takes 34 hours to return from the original road, how many kilometers per hour on average?

42 × 67 ÷ 34 = 36 × 43 = 48 (km / h). A: when returning, the average distance is 48 km / h