Question

A wall can be built by 6 men working 8 hours per day in 5 days. How many days will it take 4 men to build the same wall if they worked only 5 hours per day??

Answer 1

Total number of working hours = 6x8x5 = 240 hours
Let x be the number of days required
240 = 4(5)(x)
x = 12 days

Answer 2

its correct, but I do not understand.

Answer 3

First you need to know that the total number of working hours won't change, got it?

Answer 4

right.

Answer 5

but why multiply 6, when it repsents the number of men?

Answer 6

each man works 8 hours each day for 5 days ,and 6 men are working
That means, if only 1 man works (poor him...) , he would have to work for 8x5x6 hours to finish the whole job. He is the one who is responsible for the six men's job :S Understand so far?

Answer 7

so one man works for 240 hours?

Answer 8

to get the whole job done , yes!

Answer 9

Next, he's so lucky that there are 3 friends coming to help him. and they decide to work 5 hours a day only.
Since the number of working hours for finishing the job is unchanged, you can calculate the number of days they need to work. Got this part?

Answer 10

yes

Answer 11

So, let x be the number of days required to get the job done
total number of working hours = number of ppl x number of hours per day x number of days
240 = (4)(5)(x)
Solve x and you'll get the answer
Understand now?

Answer 12

yes

Answer 13

thank you very much.

Answer 14

lifesaver

Answer 15

welcome! Glad that you understand :)