Question

A can do a piece of work in 20 days and B can do it in 30 days. How long will they
take to do the work together?
(A)10 days
(B) 12 days
(C) 11 days
(D) 20 days
​

Answer 1

Answer:

A’s 1 day’s work = \frac{1}{20}

A’s 1 day’s work = \frac{1}{20}B’s 1 day’s work = \frac{1}{30}

A’s 1 day’s work = \frac{1}{20}B’s 1 day’s work = \frac{1}{30}∴ (A + B)’s 1 day’s work = \frac{1}{20} + \frac{1}{30} = \frac{3+2}{60} = \frac{1}{12}

A’s 1 day’s work = \frac{1}{20}B’s 1 day’s work = \frac{1}{30}∴ (A + B)’s 1 day’s work = \frac{1}{20} + \frac{1}{30} = \frac{3+2}{60} = \frac{1}{12}So, the work will be completed in 12 days if they work together.

Hence option [B] is correct answer

Step-by-step explanation:

hope it will help you

Answer 2

Answer:

A can do work in 20 days

A one day work = 1/20

B can do work in 30 days

B one day work = 1/30

A + B work

1/20 + 1/30

30 + 20/600 = 50/600

1/12days

1÷ 1/12

1*12= 12 daya