The first bricklayer can build a wall in 15 days, the second bricklayer can build the same wall in 20 days. How long will it take them to build the wall together?

Question

Mathematics

Heidi Santana

16 August, 05:36

The first bricklayer can build a wall in 15 days, the second bricklayer can build the same wall in 20 days. How long will it take them to build the wall together?

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Answers (1)

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Jasmin Kaiser · Answer 1

It takes 8 4/7 days for both bricklayers to build the wall together.

Step-by-step explanation:

The first bricklayer takes 15 days to build the wall, which means it builds 1/15 of the wall per day.

The second bricklayer takes 20 days to build the wall, which means it builds 1/20 of the wall per day.

So if they build the wall together, the expression below will tell how much of the wall they build per day together.

1/15 + 1/20

To add the fractions, we must find a common denominator, which is 60.

4/60 + 3/60, which equals 7/60.

So, they can build 7/60 of the wall per day together. How many days will it take them? We must find how many times 7 fits into 60, which can be done by solving 60/7, which is 8 4/7.

So, it takes 8 4/7 days for both bricklayers to build the wall together.