Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 1)
1.
A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :
Answer: Option
Explanation:
| A's 1 day's work = | 1 | ; |
| 15 |
| B's 1 day's work = | 1 | ; |
| 20 |
| (A + B)'s 1 day's work = |  |
1 | + | 1 |  |
= | 7 | . |
| 15 | 20 | 60 |
| (A + B)'s 4 day's work = | |
7 | x 4 | |
= | 7 | . |
| 60 | 15 |
| Therefore, Remaining work = | |
1 - | 7 | |
= | 8 | . |
| 15 | 15 |
Discussion:
344 comments Page 20 of 35.
Nagasuriya said:
10 years ago
Dear friends how to solve this calculate 7/60 x4 =7/15 please explain me?
Sunil jat kantia said:
1 decade ago
Please solve this problem.
Er.Ketan Patel said:
1 decade ago
Take LCM is 60 mean total work done is 60.
It mean "a" can do 4 unit/day, "b" can do 3 unit/day.
Total 3+4 = 7/60.
Both do work together 4 days mean (7*4=28).
They complete the work 28 (60-28=32).
32/60 = 8/15.
It mean "a" can do 4 unit/day, "b" can do 3 unit/day.
Total 3+4 = 7/60.
Both do work together 4 days mean (7*4=28).
They complete the work 28 (60-28=32).
32/60 = 8/15.
Mounika said:
1 decade ago
'1' is the total work that has to be done. (It has to be taken by default in time and work).
7/15 is (A+B) 4 day's work.
So, total work- (A+B) 's 4 day's work=work that is left to be done.
1-7/15 = 8/15.
7/15 is (A+B) 4 day's work.
So, total work- (A+B) 's 4 day's work=work that is left to be done.
1-7/15 = 8/15.
Priya said:
1 decade ago
Can any one please say, how (1-7/15) is applied?
PriyA said:
1 decade ago
But still I can't understand the logic behind the subtraction of 1. I have read @Mangesh answer. But why do we assume "one"? They did't mention anything right?
Avinash Ghadge said:
1 decade ago
@Deppa.
1/15 & 1/20 hear denominator are not same ok. So firstly we have to make both same. So 1/15 are multiply bye 4 on both numerator, denominator we get:
1*4/15*4 = 4/60.
1*3/20*3 = 3/60 this value are getting now adding this two value, we get.
4+3/60 = 7/60.
That's it. I hope you understand.
1/15 & 1/20 hear denominator are not same ok. So firstly we have to make both same. So 1/15 are multiply bye 4 on both numerator, denominator we get:
1*4/15*4 = 4/60.
1*3/20*3 = 3/60 this value are getting now adding this two value, we get.
4+3/60 = 7/60.
That's it. I hope you understand.
Devi sri prasad said:
1 decade ago
I think LCM is the best solution.
/mat said:
1 decade ago
Why 1/15, 1/20?
Akash said:
1 decade ago
Try to avoid fraction calculation.
L.C.M of(15,20) = 60.
Let total work is 60 unit.
A can do 60/15 = 4 unit/day.
B can do 60/20 = 3 unit/day.
A+B can do = 4+3 = 7 unit/day.
A+B in 4 day can do = 7*4 = 28 unit.
Total work = 60 unit.
Remaining work = 60-28 = 32 unit.
Fraction of work = (Remaining work/Total work) = 32/60 = 8/15 (ans).
L.C.M of(15,20) = 60.
Let total work is 60 unit.
A can do 60/15 = 4 unit/day.
B can do 60/20 = 3 unit/day.
A+B can do = 4+3 = 7 unit/day.
A+B in 4 day can do = 7*4 = 28 unit.
Total work = 60 unit.
Remaining work = 60-28 = 32 unit.
Fraction of work = (Remaining work/Total work) = 32/60 = 8/15 (ans).
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers