9. A completes 80% of a work in 20 days. Then B also joins and A and B together finish the remaining work in 3 days. How long does it need for B if he alone completes the work?
A. 37 ½ days
B. 22 days
C. 31 days
D. 22 days
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Let the work be X amount.
So A does 80% of X in 20 days. => 0.80 * X in 20 days.
in one day A does 0.80A / 20 = 0.04 X amount of work
A and B together complete 20% of X amount of work in 3 days.
So their productivity is : 0.20 X / 3 per day.
Productivity of B = 0.20 X/3 - 0.04 X = 0.08 X / 3 per day
B does the complete work X in : 3 / 0.08 = 37.5 days
So A does 80% of X in 20 days. => 0.80 * X in 20 days.
in one day A does 0.80A / 20 = 0.04 X amount of work
A and B together complete 20% of X amount of work in 3 days.
So their productivity is : 0.20 X / 3 per day.
Productivity of B = 0.20 X/3 - 0.04 X = 0.08 X / 3 per day
B does the complete work X in : 3 / 0.08 = 37.5 days
rajlaxmidash201:
thnx!! :)
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