Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 9)
9.
A does 80% of a work in 20 days. He then calls in B and they together finish the remaining work in 3 days. How long B alone would take to do the whole work?
23 days
37 days
37
40 days
Answer: Option
Explanation:
| Whole work is done by A in |  |
20 x | 5 |  |
= 25 days. |
| 4 |
| Now, | |
1 - | 4 | |
i.e., | 1 | work is done by A and B in 3 days. |
| 5 | 5 |
Whole work will be done by A and B in (3 x 5) = 15 days.
| A's 1 day's work = | 1 | , (A + B)'s 1 day's work = | 1 | . |
| 25 | 15 |
 B's 1 day's work = |
|
1 | - | 1 | |
= | 4 | = | 2 | . |
| 15 | 25 | 150 | 75 |
| So, B alone would do the work in | 75 | = 37 | 1 | days. |
| 2 | 2 |
Discussion:
164 comments Page 15 of 17.
Charu said:
1 decade ago
Thanks Bhasker, Ganesh and Mini... Keep up the good work!!! cheers
Vinoth said:
1 decade ago
@baskar your explations were very nice thank you so much.
Prathap said:
1 decade ago
Bhaskar and rajendra you both are explained very well. Thanks.
Nanny said:
1 decade ago
Thank you bhaskar, you done great job, keep it up.
Malinga said:
1 decade ago
How you got 80/100=5/4 ?
Biswajeet kar said:
1 decade ago
Howz 80/100=5/4?
Vaibhav said:
1 decade ago
In 20 days A does 80% work. So in one day =80/20=4%
Let we start from sunday then S M T W T F S....4% each day then total 25 days will be taken by A to 100% work done .
Similarly for A+B, in 3 days (100-80)=20% work done. for one day=20/3%..so for 100% counting on each day 15 days will come
So a+b=1/15=>b=1/15-1/20=>2/75
Let we start from sunday then S M T W T F S....4% each day then total 25 days will be taken by A to 100% work done .
Similarly for A+B, in 3 days (100-80)=20% work done. for one day=20/3%..so for 100% counting on each day 15 days will come
So a+b=1/15=>b=1/15-1/20=>2/75
Mini said:
1 decade ago
Easy Method:-
A does 80% work in 20 days= 80%/20=80/100*1/20 =1/25...(i)
A and B togheter finish the remaining work(which is 20%) in 3 days.
so (A+B) do 20% work in 3days= 20%/3=20/100*1/3 =1/15....(ii)
Now we hv to find B's Work days
So subtract equ. (ii) from (i)
(A+B)-A =1/15-1/25
B =2/75
B =37 1/2 DAYS
A does 80% work in 20 days= 80%/20=80/100*1/20 =1/25...(i)
A and B togheter finish the remaining work(which is 20%) in 3 days.
so (A+B) do 20% work in 3days= 20%/3=20/100*1/3 =1/15....(ii)
Now we hv to find B's Work days
So subtract equ. (ii) from (i)
(A+B)-A =1/15-1/25
B =2/75
B =37 1/2 DAYS
Siva said:
1 decade ago
Hi Guys,
General Concept: Time and work
A can complete work in X days
1.e., A can complete 100% of work in X Days
A's 1 day work = (Amount of work completed) /(number of days)
so,
A's 1 day work = 100%/X => 100%(1/X)
Now,
A completed 80% of work in 20 Days
so, A's 1 day work = 80%/20 => 1/25
A+B completed 20% of work in 3 days
so, (A+B)'s 1 days work = 20%/3 => 1/15
A+B = 1/15
B = (1/15-1/25) => 10/375
B's 1 day work = 100%/(10/375) => 100%(375/10)
B alone completed 100% of work in 375/10 Days
B = 37.5 Days => 37 1/2 Days
General Concept: Time and work
A can complete work in X days
1.e., A can complete 100% of work in X Days
A's 1 day work = (Amount of work completed) /(number of days)
so,
A's 1 day work = 100%/X => 100%(1/X)
Now,
A completed 80% of work in 20 Days
so, A's 1 day work = 80%/20 => 1/25
A+B completed 20% of work in 3 days
so, (A+B)'s 1 days work = 20%/3 => 1/15
A+B = 1/15
B = (1/15-1/25) => 10/375
B's 1 day work = 100%/(10/375) => 100%(375/10)
B alone completed 100% of work in 375/10 Days
B = 37.5 Days => 37 1/2 Days
Nazeem said:
1 decade ago
Great explanation by baskar. Thanks.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers