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 26 of 35.
Ashik said:
1 decade ago
Why have you taken 1 as total work? HOW?
Vamshi said:
1 decade ago
@Deepa.
(1/15+1/20) L.C.M of 15, 20 is 60.
So 1/15*60 = 4.
And 1/20*60 = 3.
4+3/60 = 7/60.
(1/15+1/20) L.C.M of 15, 20 is 60.
So 1/15*60 = 4.
And 1/20*60 = 3.
4+3/60 = 7/60.
Indu said:
1 decade ago
Short trick if you are use to of percentage:
A's 1 day's work = 6.67% (100/15).
B's 1 day's work = 5%.
A+B's 1 day's work = 11.67%.
A+B's 4 day's work = 46.68%.
Remaining... 100-46.68 = 53.33% i.e. 8/15.
A's 1 day's work = 6.67% (100/15).
B's 1 day's work = 5%.
A+B's 1 day's work = 11.67%.
A+B's 4 day's work = 46.68%.
Remaining... 100-46.68 = 53.33% i.e. 8/15.
Arpit kashyap said:
1 decade ago
A's 1 day's work = 1/15,
B's 1 day's work = 1/20,
Since they work together for 4 days so that their left work in fraction = [1 - (1/15 + 1/20)]*4.
= (8/60)*4.
= 8/15.
B's 1 day's work = 1/20,
Since they work together for 4 days so that their left work in fraction = [1 - (1/15 + 1/20)]*4.
= (8/60)*4.
= 8/15.
Viky said:
1 decade ago
I'm confused, can anybody tell me how 7/60 came?
Shiva said:
1 decade ago
@Kiran.
(1/15+1/20) = (20+15)/300 //This get by cross multiplication.
= 35/300.
= 7/60.
I think your doubt is clear now.
(1/15+1/20) = (20+15)/300 //This get by cross multiplication.
= 35/300.
= 7/60.
I think your doubt is clear now.
Kiran said:
1 decade ago
Can you explain How you got = (1/15+1/20) = 7/60?
Sowmi said:
1 decade ago
Why the value of b had multiplied but in final there is a subtraction is held?
Geek said:
1 decade ago
1-((1/20+1/15)*4)==>1-7/15==>8/15.
This is easy method, I think. If any other easy method please give me.
This is easy method, I think. If any other easy method please give me.
Mukesh Mishra said:
1 decade ago
A's 1 day work=1/15; B's 1 day work = 1/20.
OK. Then we calculate how much A + B can do in 1 day.
i.e. 1/15 + 1/20 ( in fraction if denominator is different first we find the l.c.m of denominator). So we calculate the l.c.m of 15 and 20 i.e 60(15 and 20 is divided by 5 we get the answer 3 and 4 so we find l.c.m by multiplying 5*3*4=60). 1/15*60+1/20*60 = 4+3/60 = 7/60.
If A and B do work in 4 days = 7/60*4 = 7/15.
Remaining work = 1-7/15 = 8/15 [ (15*1-7)/15 = 8/15.
OK. Then we calculate how much A + B can do in 1 day.
i.e. 1/15 + 1/20 ( in fraction if denominator is different first we find the l.c.m of denominator). So we calculate the l.c.m of 15 and 20 i.e 60(15 and 20 is divided by 5 we get the answer 3 and 4 so we find l.c.m by multiplying 5*3*4=60). 1/15*60+1/20*60 = 4+3/60 = 7/60.
If A and B do work in 4 days = 7/60*4 = 7/15.
Remaining work = 1-7/15 = 8/15 [ (15*1-7)/15 = 8/15.
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