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 3 of 35.
Sujit said:
1 decade ago
@Dipen:
Probability is always .....Total chance = 1.
If you say chances of wining a match is 1/2 i.e.(50%) it means chances of losing match is also 1/2 (50%)...how this losing chances 1/2 comes?
It comes from subtracting wining chances from total chance that is : 1-1/2 = 1/2
Similarly in above question
Remaining work = total work (1) - 4 day's work (7/15) = 8/15
Hope you get this...Have a great time :-)
Probability is always .....Total chance = 1.
If you say chances of wining a match is 1/2 i.e.(50%) it means chances of losing match is also 1/2 (50%)...how this losing chances 1/2 comes?
It comes from subtracting wining chances from total chance that is : 1-1/2 = 1/2
Similarly in above question
Remaining work = total work (1) - 4 day's work (7/15) = 8/15
Hope you get this...Have a great time :-)
Dipu Ahmed said:
9 years ago
Here,
A works 1/15 in 1 day.
B works 1/20 in 1 day.
So, A + B works (1/15 + 1/20) = 7/60 in 1 day.
So, if A + B works together 7/60 in 1 day.
Then A + B works together (7/60 * 4) = 8/15 in 4 day.
If we assume that 1 is the full work and A+B works together 8/15 in 4 days .
The remaining works we get by {full work - (A + B)'s 4 days completed works}.
So , (1 - 8/15) = 7/15.
So, the answer is 7/15.
A works 1/15 in 1 day.
B works 1/20 in 1 day.
So, A + B works (1/15 + 1/20) = 7/60 in 1 day.
So, if A + B works together 7/60 in 1 day.
Then A + B works together (7/60 * 4) = 8/15 in 4 day.
If we assume that 1 is the full work and A+B works together 8/15 in 4 days .
The remaining works we get by {full work - (A + B)'s 4 days completed works}.
So , (1 - 8/15) = 7/15.
So, the answer is 7/15.
Krishna gummani said:
1 decade ago
A can do a work in 15 days.
B can do the work in 20 days.
i.e. in one day the work completed by A and B is 1/15 and 1/20 respectively.
In one day the work done by both A and B is, 1/15+1/20 = 7/60.
If, for one day the work done is 7/60, then for four days?
7/60*4 = 28/60.
The total work is 1.
Work done in 4 days is 28*60.
Then, remaining work is to be done is 1-28/60.
i.e. 8/15.
Hence proved.
B can do the work in 20 days.
i.e. in one day the work completed by A and B is 1/15 and 1/20 respectively.
In one day the work done by both A and B is, 1/15+1/20 = 7/60.
If, for one day the work done is 7/60, then for four days?
7/60*4 = 28/60.
The total work is 1.
Work done in 4 days is 28*60.
Then, remaining work is to be done is 1-28/60.
i.e. 8/15.
Hence proved.
Joel said:
4 years ago
Lets take total work is = 1.
In 15 days A will complete the work;
In one day he comlete 1/15 part of work,
Similarly B comletes 1/20 work in one day.
Hence A and B both completes 1/15 + 1/20 work in one day
1/15+1/20 = 7/60.
A and B's one day work,
thier 4 days work = 4 * (7/60) = 28/60 = >7/15,
Now total work is 1,
They completed 7/15 work in 4 days,
Now remaining work is1-7/15 = 8/15.
In 15 days A will complete the work;
In one day he comlete 1/15 part of work,
Similarly B comletes 1/20 work in one day.
Hence A and B both completes 1/15 + 1/20 work in one day
1/15+1/20 = 7/60.
A and B's one day work,
thier 4 days work = 4 * (7/60) = 28/60 = >7/15,
Now total work is 1,
They completed 7/15 work in 4 days,
Now remaining work is1-7/15 = 8/15.
Dibyanshu said:
3 years ago
A - 15 days.
B - 20 days.
LCM of 15 & 20 is 60 (The total work is 60 also).
So,
The Efficiency of one day's work is 60/15 = 4 and 60/20 = 3.
Then, both A & B can complete the work in one day is 4+3=7.
They worked for 4 days, so 7x4=28
Work completed in 4days by both A+B=28.
Then, rest work = Total work - Completed work
Rest work = 60-28=32.
32/60 = 8/15
The answer is = 8/15.
B - 20 days.
LCM of 15 & 20 is 60 (The total work is 60 also).
So,
The Efficiency of one day's work is 60/15 = 4 and 60/20 = 3.
Then, both A & B can complete the work in one day is 4+3=7.
They worked for 4 days, so 7x4=28
Work completed in 4days by both A+B=28.
Then, rest work = Total work - Completed work
Rest work = 60-28=32.
32/60 = 8/15
The answer is = 8/15.
(233)
Ankit kain said:
8 years ago
Here is the perfect solution.
L.C.M- 60 (it is the lcm of 15 and 20 and here it is total work)
A's---------15 days|---EFFICIENCY-60÷15=4 (because, work= efficiency * time)
B's---------20 days|---EFFICIENCY-60÷20=3
combined efficiency of A and B =7.
work done by (A+B) in 4 days= 7 * 4=28(because work = efficiency * time).
hence ratio---------> 28/60=8/15.
L.C.M- 60 (it is the lcm of 15 and 20 and here it is total work)
A's---------15 days|---EFFICIENCY-60÷15=4 (because, work= efficiency * time)
B's---------20 days|---EFFICIENCY-60÷20=3
combined efficiency of A and B =7.
work done by (A+B) in 4 days= 7 * 4=28(because work = efficiency * time).
hence ratio---------> 28/60=8/15.
Mahesh Gehlot said:
1 decade ago
7/60 is the total work done by A and B in day 1.
Therefore for 4 days we will calculate as below.
7/60 *4 means when its multiplication we will divide.
ie. 4/15 = 60 and we need to keep 7 integer as it was.
Therefore we get 7/15.
I don't know, Hope you'll understand this.
A simple logic when its + or - we will cross multiply
And when its * we will divide.
Thanks.
Therefore for 4 days we will calculate as below.
7/60 *4 means when its multiplication we will divide.
ie. 4/15 = 60 and we need to keep 7 integer as it was.
Therefore we get 7/15.
I don't know, Hope you'll understand this.
A simple logic when its + or - we will cross multiply
And when its * we will divide.
Thanks.
RDT said:
1 decade ago
@KARTHIKEYAN and @RAHUL.
DONT CONFUSE.
A can do in 15 days.
A can do it in 1 days = 1/15.
Similarly B can do it = 1/20.
They work totally in a day.
1/15+1/20 = 35/300 = 7/60.
Work done by A and B for 4 days = 4(7/60) = 7/15.
So, Work left = Total work - Work done by A and B.
Therefore, work left = 1-(7/15) = 8/15.
This is the answer.
I hope this helps you.
DONT CONFUSE.
A can do in 15 days.
A can do it in 1 days = 1/15.
Similarly B can do it = 1/20.
They work totally in a day.
1/15+1/20 = 35/300 = 7/60.
Work done by A and B for 4 days = 4(7/60) = 7/15.
So, Work left = Total work - Work done by A and B.
Therefore, work left = 1-(7/15) = 8/15.
This is the answer.
I hope this helps you.
Thyag said:
1 decade ago
Hi Manoj,
You need to simplify big number 35/300 in to small number for further calculation.
So, you need to divide one common number of both numerator and denominator.
You couldn't select 2, 3 and 4 as a dividing number. But you can use 5 as a common divider.
If you divide 5 in both numerator and denominator, you will get 7/60.
I hope your doubt clarified.
You need to simplify big number 35/300 in to small number for further calculation.
So, you need to divide one common number of both numerator and denominator.
You couldn't select 2, 3 and 4 as a dividing number. But you can use 5 as a common divider.
If you divide 5 in both numerator and denominator, you will get 7/60.
I hope your doubt clarified.
Ram said:
1 decade ago
Hi friends..........
A can do wrk in 15 dayz ;
b Can do wrk in 20 dayz;
then LCM of A&B=7/60;
Explain:
=1/15+1/20
=[(4/4*15)+(3/3*20)]
=(4/60)+(3/60)
=3+4/60
=7/60
If A and B do wrk in 4 day=(7/60 *4 )
=7/15
work is 1 so=1-7/15
=15-7/15
Ans is = 8/15
Its easy for ur understanding...............
A can do wrk in 15 dayz ;
b Can do wrk in 20 dayz;
then LCM of A&B=7/60;
Explain:
=1/15+1/20
=[(4/4*15)+(3/3*20)]
=(4/60)+(3/60)
=3+4/60
=7/60
If A and B do wrk in 4 day=(7/60 *4 )
=7/15
work is 1 so=1-7/15
=15-7/15
Ans is = 8/15
Its easy for ur understanding...............
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