doubt clearence?

Question

Piece of work?

A can complete a piece of work in 15 days , working 8 hours a day . The work is started by A on the first day . On the second day ,one man ,whose capacity is twice that of A , is added.On the third day ,another man ,whose capacity is thrice that of A, is added and so on. In how many days will the work be completed , if everyone works for exactly one hour a day ?



what it means when we say "......On the second day ,one man ,whose capacity is twice that of A ...." in this context ?


what it means when we say ".....On the third day ,another man ,whose capacity is thrice that of A....."


please clear this doubt ......this is not understandable

Answer 1

"On the second day ,one man ,whose capacity is twice that of A" means that the second man can work twice as fast as the first man, "A". (Using letters to name these guys is dumb, IMO.)

"On the third day ,another man ,whose capacity is thrice that of A" means that the third man can work three times as fast as the first man.

"And so on" means that on the fourth day, a fourth man will be added that can work 4 times as fast as the first man; on the 5th day, a 5th man will be added that can work 5 times as fast as the 1st man; etc.

So, the first day, the 1st guy who can do the job in 15 8-hour work days works one hour. He completes 1/120 (5/6 % or 0.83%) of the work, since it normally would take him 15*8 = 120 hours to do the whole thing.

2nd day: 2nd guy who is twice as fast (i.e., he could do job in 60 hours) is added. But 1st guy also works another hour. So, you have 1st guy's 1st day's work (0.83%), 1st guy's 2nd day's work (0.83%), and 2nd guy's 2nd day's work (1.67%). Adding these up, you get that after 2 days, 3.33% of the work is done.

3rd day: 1st guy will have worked 3 days (3*0.83%), 2nd guy will have worked 2 days (2*1.67%), and 3rd guy, who can do whole job in 40 days will add his 1/40 (2.5%). Total work done: 8.33%

4th day:
1st guy (4*0.83%)
2nd guy (3*1.67%)
3rd guy (2*2.50%)
4th guy (1*(1/30) = 3.33%)
Total work done: 16.67%

Answer 2

Twice means 2 times as much capacity as A

Thrice means 3 times as much capacity as A.