Question

John and Joshua can complete a task in 10 and 20 days both of them start to work together but after 3 days Joshua went somewhere.

Answer 1

Given :- John and Joshua can complete a task in 10 and 20 days both of them start to work together but after 3 days Joshua went somewhere. In how many days task was completed . ?

Solution :-

→ LCM of 10 and 20 = 20 units = Let complete task .

then,

→ Efficiency of John = 20/10 = 2 unit/day .

→ Efficiency of Joshua = 20/20 = 1 unit/day.

so,

→ Efficiency of both = (2 + 1) = 3 unit/day.

then,

→ in 3 days both completes = 3 * 3 = 9 unit of task.

So,

→ Task left to be done alone by John now = 20 - 9 = 11 units .

therefore,

→ Time taken by John to complete rest task = 11/2 = 5.5 days.

hence,

→ Total time taken to complete the task = 5.5 + 3 = 8.5 days. (Ans.)

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Answer 2

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A does a job in 10 days ⟹A does 110 of job per day.

B does a job in 20 days ⟹B does 120 of job per day.

Every 2 days, A and B do 110+120=320 of job or an average of 340 of job per day.

⟹403=1313

In first 13 days, A and B have done⟹710+620=1 full job.

It will take exactly 13 days to finish the work.