A and B drive from a to B. A goes for one hour at the speed of 32 km / h, and then B starts. It is known that B's speed is 40 km / h. how many hours has it taken b to catch up with a? It is required to be a linear equation of one variable

A and B drive from a to B. A goes for one hour at the speed of 32 km / h, and then B starts. It is known that B's speed is 40 km / h. how many hours has it taken b to catch up with a? It is required to be a linear equation of one variable

Let car B catch up with car a after X hours
Equivalency: the distance of car B = the distance of car a
Or a + 32 = b
So 32 + 32x = 40x
8X=32
X=4
A: car B overtakes car a after 4 hours

The distance between Party A and Party B is 135 km. A car from Party A to Party B, originally planned to travel m km per hour, but actually speed up 3 km per hour. After speeding up, it can reach Party B several hours ahead of time

Original planned time: 135 / M hours
Actual speed per hour: (M + 3) km
Actual time: 135 / (M + 3) hours
advance:
135/m-135/(m+3)
=135*(m+3-m)/[m(m+3)]
=405 / [M (M + 3)] hours

A 1920m long highway was built by two engineering teams, team a and team B. first, team a built the highway at a speed of 30m per day for several days, and then team B built it again. Team B built the highway 45m per day, and the two teams shared 50 days to complete the construction. How many days did team a and team B build the highway respectively

Let a repair X days 30x + (50-x) * 45 = 1920 30x + 2250-45x = 1920 30x-45x = 1920-2250
-15x = - 330 x = 22 B: 50-22 = 28

A factory has m tons of coal and plans to use n tons every day. Now, in response to the call of national energy conservation and emission reduction, if a ton of coal is actually saved every day, these coal can be actually used___ Day

∵ there are m tons of coal in a factory. It is planned to use n tons of coal every day. In fact, a ton of coal is saved every day. The actual available days of these coal are: mn-a; so the answer is: mn-a