If 10 men can construct a building in 40 days.
How long will it take 20 men to do this work?
20v
Answers
Answer: 20 days
Step-by-step explanation:
There are three ways in which you can solve this question.
METHOD 1
This question can be easily solved by applying some common sense.
10 men can construct a building in 40 days. Now, the same building has to be constructed by 20 men. It is obvious that in this case, the number of days will be less.
If more people are employed to do the same thing, the work will get finished faster. So, the number of days taken to finish the work is less.
The number of men is doubled that means the number of days will be halved, that is, half of 40 days which is 20 days.
METHOD 2
Note - For this method to use, you must be familiar with direct and indirect variation.
Here, the number of men and the number of days is inversely proportional because increasing the number of workers will help in finishing the work in less time.
When two things are inversely proportional, their product is always constant.
Let the number of days 20 men take be = y
20 × y = 10 × 40
y = 400/20
y = 20
Therefore, 20 men will take 20 days to construct 1 building.
METHOD 3
Note - For this method to use, you must be familiar with the unitary method.
10 men can construct a building in 40 days. So, they can construct 1/40th of the building in 1 day.
40 days → 1 building
1 day → 1/40 building (Unitary Method)
So, in 1 day, 10 men can construct 1/40 building. So 1 man can construct 1/400 building in one day.
10 men → 1/40 building
1 man → 1/400 building
Now, we have to find how many(or how much) building can be constructed in 1 day by 20 men.
1 man → 1/400 building
20 men → 1/20 building
20 men can build 1/20 building in one day. Let's calculate how many days do 20 men need to construct 1 building.
1/20 building → 1 day
1 building → 20 days.
Therefore, 20 men need 20 days to complete constructing one building.
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20 days will be your answer
Step-by-step explanation:
There are three ways in which you can solve this question.
METHOD 1
This question can be easily solved by applying some common sense.
10 men can construct a building in 40 days. Now, the same building has to be constructed by 20 men. It is obvious that in this case, the number of days will be less.
If more people are employed to do the same thing, the work will get finished faster. So, the number of days taken to finish the work is less.
The number of men is doubled that means the number of days will be halved, that is, half of 40 days which is 20 days.
METHOD 2
Note - For this method to use, you must be familiar with direct and indirect variation.
Here, the number of men and the number of days is inversely proportional because increasing the number of workers will help in finishing the work in less time.
When two things are inversely proportional, their product is always constant.
Let the number of days 20 men take be = y
20 × y = 10 × 40
y = 400/20
y = 20
Therefore, 20 men will take 20 days to construct 1 building.
METHOD 3
Note - For this method to use, you must be familiar with the unitary method.
10 men can construct a building in 40 days. So, they can construct 1/40th of the building in 1 day.
40 days → 1 building
1 day → 1/40 building (Unitary Method)
So, in 1 day, 10 men can construct 1/40 building. So 1 man can construct 1/400 building in one day.
10 men → 1/40 building
1 man → 1/400 building
Now, we have to find how many(or how much) building can be constructed in 1 day by 20 men.
1 man → 1/400 building
20 men → 1/20 building
20 men can build 1/20 building in one day. Let's calculate how many days do 20 men need to construct 1 building.
1/20 building → 1 day
1 building → 20 days.
Therefore, 20 men need 20 days to complete constructing one building.