Question

MATHEMATICAL SKILLS
A and B can separately do a piece of work in 20 and 15 days, respectively. They
worked together for 6 days, after which B was replaced by C. If the work was
finished in the next 4 days, then the number of days in which C alone could do
the work
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Answer 1

Answer:

6*(1/20 + 1/15) = 3/10 + 4/10 = 7/10

After 6 days, 7/10 is made and 3/10 left.

4/20 = 2/10

That’s the work A made in 4 days.

The rest of the work is 1/10… which is made by C in 4 days.

So, 4*(1/x) = 1/10

x = 40.

C alone would need 40 days.