Discussions
Ravi Tej

· started a discussion

· 1 Months ago

how it could be 10? its 5 know

Knowledge Expert

· commented

· 1 Months ago

Dear student,
We have updated the solution.
Keep learning,
Team TR
Pratik Bhattacharjee

· started a discussion

· 1 Months ago

how come the answer is 10 days?

Question:
A and B can do a work in 12 days ,B and C in 15 days and C and A in 20 days. If A, B and C work together, they will complete the work in :
Options:
A) 5 days.
B) \(7\cfrac{5}{6}\) days.
C) 10 days.
D) \(15\cfrac{2}{3}\) days.
Solution:

Ans (c)

According to question,

A and B can do a work in 12 days 

\(\therefore\) (A + B)'s one days' work = \(\cfrac{1}{12}\)

Similarly,

(B+C)'s one day's work = \(\cfrac{1}{15}\)

and (C+A) one day's work = \(\cfrac{1}{20}\)

an adding all three,

\(=\cfrac{1}{12}+\cfrac{1}{15}+\cfrac{1}{20}=\cfrac{5+4+3}{60}=\cfrac{1}{5}\)

2(A+B+C)=\(\cfrac{1}{5}\)

Thus,

A+B+C=\(\cfrac{1}{5*2}\)=\(\cfrac{1}{10}\)

(A+B+C)'s one day's work = \(\cfrac{1}{10}\)

\(\therefore\) A,B and C together can finish the whole work in 10 days