Question

in 18 days, 20 workers can build a school. How many days would it take if there were only 12 workers?​

Answer 1

To build a school;

20 workers -> 18 days.

So 1 worker -> 18/20 days.

So; 12 workers -> (12×18)/20 days.

-> (12×9)/10 days

->10.8 days.

so 10.8 days is your answer.

Hope it helps...

Regards;

Leukonov/Olegion

Answer 2

☯ Appropriate Question -:

If 20 workers can build a school in 18 days, how many days will it take 12 workers to build the same school?

☯ Step-by-step explanation -:

In this question we are provided that 20 workers can build a school in 18 days. We are asked to calculate how many days will 12 workers will take to do the same work.

We can solve this question using two methods :

• Unitary Method
• Method of proportion

`\small\bf{ Unitary \: Method}`

20 workers can build a school in 18 days

1 worker can build a school in 20 × 18 days

12 workers can build a school in
`(20 × 18 )/(12)` = 30 days.

• Hence the required number of days is 30.

`{{\rule{40mm}{4pt}}}`

`\small\bf{ Method \: of \: proportion }`

Let us assume that 12 workers can finish the work in x days.

`\begin{array}c \bf{Number \: of \: workers }& \bf{Number \: of \: days}\\ 20 & 18 \\ 12 & x\end{array}`

Ratio of workers = Inverse ratio of days

`\small\sf{ 20 : 12 :: x : 18}`

Product of mean = Product of extreme

`\small\rm{ 12 * x = 20 * 18}`

`\small \rm{ (20 * 18)/(12) = 30 \: days}`

• Hence the required number of days is 30.

`\rule{72mm}{5pt}`