A and b can do a piece of work in 30 days. they work together for 20 days, then b left the work. rest work a alone complete the work in extra 20 days . then find in how many days b alone can finish the work.
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A can complete a piece of work in 30 days. Bcan complete a piece of work in 20 days.
Therefore the total units of work will be the LCM of both 20 & 30 = 60 units
Therefore, no of units of work per day by A =60/3 = 2 units
Similarly, no of units of work per day by B = 60/3 = 3 units.
They start working together and B will leaves 5 days before the work is finished. — (1)
Therefore for the last 5 days only A does the work and total number of units of work done by A in those last 5 days is = 2 units * 5 = 10 units.
Now total number of units of work left = 60 - 10 =50 units.
Total number of units of work per day done by A & B together = 2 units + 3 units = 5 units
Therefore total number of days A & B worked together = 50/5 = 10 days. — (2)
Therefore total number of days taken to work = 5 + 10 = 15 days.
Therefore the total units of work will be the LCM of both 20 & 30 = 60 units
Therefore, no of units of work per day by A =60/3 = 2 units
Similarly, no of units of work per day by B = 60/3 = 3 units.
They start working together and B will leaves 5 days before the work is finished. — (1)
Therefore for the last 5 days only A does the work and total number of units of work done by A in those last 5 days is = 2 units * 5 = 10 units.
Now total number of units of work left = 60 - 10 =50 units.
Total number of units of work per day done by A & B together = 2 units + 3 units = 5 units
Therefore total number of days A & B worked together = 50/5 = 10 days. — (2)
Therefore total number of days taken to work = 5 + 10 = 15 days.
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