Question

solve in step by step........................​

Answer 1

Answer:

(a) 10 days

Hope this helps!

Step-by-step explanation:

Let a be A's working speed, in "pieces of work per day".

Let b be B's working speed, in "pieces of work per day".

Let c be C's working speed, in "pieces of work per day".

Then...

A and B together take 12 days for one "piece of work"

=> a + b = pieces of work / number of days = 1 / 12

B and C together take 15 days for one "piece of work"

=> b + c = pieces of work / number of days = 1 / 15

C and A together take 20 days for one "piece of work"

=> c + a = pieces of work / number of days = 1 / 20

Adding these three equations, we get

a + b + b + c + c + a = 1/12 + 1/15 + 1/20 = 5/60 + 4/60 + 3/60 = 12/60 = 1/5

=> 2 ( a + b + c ) = 1/5

=> a + b + c = 1/10

=> The combined speed of A, B and C together is 1/10 "pieces of work per day"

=> Together, A, B and C take 10 days to do the one piece of work.