A) 10 days
B) 20 days
C) 15 days
D) 6 days
Correct Answer: A
Solution :
A's 1 day's work\[=\frac{1}{20}\] A's 4 days work\[=\frac{4}{20}=\frac{1}{5}\] Remaining work\[=1-\frac{1}{5}=\frac{4}{5}\] This part is completed by A and B together. Now, (A + B)?s 1 day's work \[=\frac{1}{20}+\frac{1}{12}\] \[=\frac{3+5}{60}=\frac{8}{60}=\frac{2}{15}\] Now, \[\frac{2}{15}\]work is done by (A + B) in 1 day. \[\therefore \]\[\frac{4}{5}\]work is done in \[=\frac{15}{2}\times \frac{4}{5}=6\]days. Hence, the work lasted for\[4+6=10\]days.You need to login to perform this action.
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