Time speed, work, Alligations and mixtures problems

eagles_dare13 · **help in DI -** 30-05-2005, 03:18 PM

without multiplying actually, is there a way to tell which is greater ..
say 61*94 and 92 * 65.
This comes in handy in DI.
Also , please tell me exactly how remebering reciprocals upto 30 will fhelp.
becasue i can calculate percentages by adjusting numerator and denominator until the denom is 100.

vkakkar · **Query -** 30-05-2005, 03:18 PM

Is the answer of 2nd question "25 days".??
PLs let me know the correct answer so tht i can help.

Quote:

Originally Posted by madhavi

Questions on Time and Work

1. 20 women can finish a job in 20 days. After each day, one woman is replaced by a man or a boy alternatively starting with a man.Man is twice efficient and boy is half efficient as a woman,On which day does the job get completed??

2. A can do a job in 10 days. B can do the same job in 15 days. C can demolish the same job in 20 days. In how many days does the work get completed, if C starts the work and they work on alternate days as C-A-B-C and so on.

rajsher · 30-05-2005, 03:22 PM

Quote:

Originally Posted by madhavi

Questions on Time and Work

1. 20 women can finish a job in 20 days. After each day, one woman is replaced by a man or a boy alternatively starting with a man.Man is twice efficient and boy is half efficient as a woman,On which day does the job get completed??

2. A can do a job in 10 days. B can do the same job in 15 days. C can demolish the same job in 20 days. In how many days does the work get completed, if C starts the work and they work on alternate days as C-A-B-C and so on.

Q1. 400 women hours r required.
there r 20 women hours every day.
If we replace by a man, then count goes up by 1 and if v replace by a boy count comes down by 0.5, so the series is--
20+21+20.5+21.5+21+22+21.5+22.5+22+23+22.5+23.5+23 +24+23.5+24.5+24+18(25)=400

so no. of days = 17+(18/25) = 17.72 days answer.

Q2. Can u clear on C's part. i mean if he has to demolish what will he do on the first day????

MrAnderson · 03:44 PM

1. 20 women can finish a job in 20 days. After each day, one woman is replaced by a man or a boy alternatively starting with a man.Man is twice efficient and boy is half efficient as a woman,On which day does the job get completed??

2. A can do a job in 10 days. B can do the same job in 15 days. C can demolish the same job in 20 days. In how many days does the work get completed, if C starts the work and they work on alternate days as C-A-B-C and so on.

1.assume total work = 800 units.
so a woman does 2 units of work in a day
man ..4 units...boy ..1 unit...

starting with 20 women intially..
day 1...40 units completed
day 2...38 + 4 = 42 units
day 3 ..36 + 1 + 4 = 41 units
day 4 ..34 + 1 + 8 = 43 units ..etc etc
day 5 ..32 + 2 + 8 = 42
day 6 ..30 + 2 +12 =44
now we hv to find in how many days this will add to 800 ...
easy way to do tht...
day 1 + day 2 = 82
day 3 + day 4 = 84
day 5 + day 6 = 86 ..etc... AP

in 18 days ... total work done = 9 (164 + 8*2)/2 = 9 (90) = 810
so work gets over on the 18th day...(u can calculate xact duration also)

2. assume 300 units of work..
so A = 30 units/day
B = 20 units/day
C = -15 units/day ...
so in a cycle of 3 days..cab total work done = 35 ...
in 8 cycles(24 days) .. 280 units .... 25 th day .. -15 ..so 265 ..then +30 ...295
on the 27 th day 5 units remaining..and B finfishes 20 units per day..
so in 1/4 of the day he will finish the work...
so ans 26.25 days.

edited: saw rajsher's post only after posting...good point..wht did C do on day 1....
did he mess things up so tht A had to do some cleaning up b4 starting work??

..int ht case my soln is right..else.. we hv to take day 1 as 0...and count taking
nxt 3 days.....so ans wud be..25 2/3 as given...

andy .

rajsher · 03:36 PM

Quote:

Originally Posted by madhavi

Questions on Time and Work

2. A can do a job in 10 days. B can do the same job in 15 days. C can demolish the same job in 20 days. In how many days does the work get completed, if C starts the work and they work on alternate days as C-A-B-C and so on.

If we take this question as it is then answer is---

Day 1 - 0
next three days 1/10 + 1/15 - 1/20 = 7/60

so till 25 days work done is 56/60 and work left is 1/15

so the next day A will finish in (1/15)/(1/10) = 2/3 days

So answer 25 2/3 days

madhavi · 30-05-2005, 03:29 PM

The correct answer is 25 2/3 days.

Quote:

Originally Posted by vkakkar

Is the answer of 2nd question "25 days".??
PLs let me know the correct answer so tht i can help.

mr_quipster · 30-05-2005, 03:35 PM

Quote:

Originally Posted by madhavi

The correct answer is 25 2/3 days.

thoda vistaar poorvak batao devi

rajsher · 30-05-2005, 03:39 PM

Quote:

Originally Posted by mr_quipster

thoda vistaar poorvak batao devi

C the post number 15 above.
If u dont understand then main thoda aur vistaar se bataa doonga

cheers,
Rajsher

Zorro · 30-05-2005, 03:41 PM

In 3 days..work done = 7/60.

The Catch: C Starts with Zero work.. so he has nothing to demolish.
so in day 1 C does Zero Work. so the Patter is ABC..ABC....

In 24 days.. work done = 56/60...
so work left is 1/15. and days passed is 25.

Time taken by a to complete 1/15 th of work is 10/15 = 2/3

ie 252/3 days... pls correct me

1/15...

Quote:

Originally Posted by rajsher

If we take this question as it is then answer is---

Day 1 - 0
next three days 1/10 + 1/15 - 1/20 = 7/60

so till 25 days work done is 56/60 and work left is 1/15
so next day, work left will be 1/15-1/20 = 1/60

next day a will finish in 1/6 days

So answer is 26 1/6 days