Question

Jagdish can build a wall in 10 days. Narender can build the same wall in 12 days while Sumit takes 15 days to do the same job. Which two of them should be employed to finish the job in 6 days?

Answer 1

Hint: For solving this question you should know about the efficiency of someone and how to calculate this. In this problem we will find the efficiency of per person and then we will compare them with each other and then we will find the final efficiency by adding any two from all these three.

Complete step-by-step solution:
According to our question, Jagdish builds a wall in 10 days, Narender can build the same wall in 12 days and Sumit takes 15 days to build the same wall. Now it is asked to find the two of them who will do this same work together within 6 days. So, if we find the efficiency of all the workers, then we can find the work they can do in one day. And this work done in one day is known as efficiency for that. And if we calculate the efficiency for Jagdish, then,
The work done by Jagdish in one day $=\dfrac{1}{10}$
Then we follow the same procedure for Narender.
So, efficiency of Narender $=\dfrac{1}{12}$
And the work done by Sumit in one day $=\dfrac{1}{15}$
Now we are asked to find any two persons who can do the same work together in 6 days. Then for this, we will add the efficiency of Jagdish and Sumit. So, we get,
$=\dfrac{1}{10}+\dfrac{1}{15}=\dfrac{3+2}{30}=\dfrac{5}{30}=\dfrac{1}{6}$
So, both Sumit and Jagdish can do it within 6 days.

Note: While solving the efficiency we always divide 1 by the number of days in which that task is going to be completed. And this is known as per day efficiency. But if two or more persons work together then the efficiency of all will be added together because they are all working with each other and due to this the work will be completed soon.