Question

Anand is twice as efficient as Bala. Bala can complete a job in $30$days. Find the number of days in which both Anand and Bala can complete it.
A. $10$
B. $8$
C. $6$
D. $12$

Answer 1

Hint: Firstly, we will assume Bala work will be x days. We will find one day work of Bala and then one day work of Anand. Further we will add Bala and Anand work, to get the desired result.

Complete step-by-step answer:
Let Bala complete a work in $ = x$ days
According the question
So, Anand complete a work in $ = 2x$days
Now,
In $30$ days Bala completes a work$ = x$.
One day work of Bala $ = \dfrac{x}{{30}}$
One day work of Anand $ = \dfrac{{2x}}{{30}}$
$ \Rightarrow $ One day work of Anand$ = \dfrac{x}{{15}}$
Then,
One day work of both Anand and Bala $ = \dfrac{x}{{30}} + \dfrac{x}{{15}}$
One day work of both Anand and Bala $ = \dfrac{{2x + x}}{{30}}$
One day work of both Anand and Bala $ = \dfrac{{3x}}{{30}}$
One day work of both Anand and Bala $ = \dfrac{x}{{10}}$
Therefore, both can complete work in $10$days.

Note: Students must know that one day work means $1$divide by complete work. And efficiency is always reciprocal of work or capacity.