Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 23)
23.
A and B can do a piece of work in 30 days, while B and C can do the same work in 24 days and C and A in 20 days. They all work together for 10 days when B and C leave. How many days more will A take to finish the work?
Answer: Option
Explanation:
| 2(A + B + C)'s 1 day's work = |  |
1 | + | 1 | + | 1 |  |
= | 15 | = | 1 | . |
| 30 | 24 | 20 | 120 | 8 |
| Therefore, (A + B + C)'s 1 day's work = | 1 | = | 1 | . |
| 2 x 8 | 16 |
| Work done by A, B, C in 10 days = | 10 | = | 5 | . |
| 16 | 8 |
| Remaining work = | |
1 - | 5 | |
= | 3 | . |
| 8 | 8 |
| A's 1 day's work = | |
1 | - | 1 | |
= | 1 | . |
| 16 | 24 | 48 |
| Now, | 1 | work is done by A in 1 day. |
| 48 |
| So, | 3 | work will be done by A in | |
48 x | 3 | |
= 18 days. |
| 8 | 8 |
Discussion:
61 comments Page 2 of 7.
Sandeep said:
1 decade ago
While calculating A's 1days work, (1/16-1/24) =1/48.
Why we are taking 1/24 ?
Why we are taking 1/24 ?
Vamsintr said:
1 decade ago
A+B+C=1/16, B+C=1/24.
(A+B+C) - (B+C) =1/16-1/24.
By solving we get 1/48.
(A+B+C) - (B+C) =1/16-1/24.
By solving we get 1/48.
(1)
Surya said:
1 decade ago
A+B=1/30 AND B+C=1/24 AND C+A=1/20.
As per question all work together means : a+b+b+c+c+a=2a+2b+2c;
2 is common factor so we can write it as 2(a+b+c).
As per question all work together means : a+b+b+c+c+a=2a+2b+2c;
2 is common factor so we can write it as 2(a+b+c).
Sudarshan yadav said:
1 decade ago
2(a+b+c) 1 days work =1/8 then a+b+c 1 day work=1/16 then a's 1 day work=1/16-1/24=1/48 then in 10 days a+b+c can do 10/16 work now remaining work=1-10/16=3/8 now in 48 days a can do 1 work then 3/8 work a can do in 48*3/8=18.
Vanmathi said:
1 decade ago
How we wrote the third step?
Manu said:
1 decade ago
Nice work guys. I really didn't understand how we calculated A's one days work 1/48 but after reading discussions I got the answer, nice work by all of you.
Phanikiran said:
1 decade ago
What @Naveen kumar said is good and really simple to understand even though it's somewhat long. But no problem. Thank you dude.
Nandhakumar said:
1 decade ago
how to find A's 1's day work
(1)
Anandhi said:
1 decade ago
A+B+C one day work = 1/16.
Given B+C = 1/24.
Therefore A+B+C = 1/16.
A+1/24 = 1/16.
A = 1/16-1/24.
A = 1/48.
Given B+C = 1/24.
Therefore A+B+C = 1/16.
A+1/24 = 1/16.
A = 1/16-1/24.
A = 1/48.
(2)
Nikhil said:
1 decade ago
A+B = 30 days.
B+C = 24 days.
C+A = 20 days.
--------------------
divide by taking lcm (30,24,20) = 120.
A+B = 4 units.
B+C = 5 units.
C+A = 6 units.
-------------------
2( A+B+C) = 15 units.
A+B+C =7.5 units.
They work together 10 days, means in 10 days they have completed 75 units out of 120 units. now,
Remaining units are (120-75) = 45.
A+B+C = 7.5 (put B+C= 5 as given),
A = 2.5.
So for completing 45 units, A need (45/2.5) = 18 days.
B+C = 24 days.
C+A = 20 days.
--------------------
divide by taking lcm (30,24,20) = 120.
A+B = 4 units.
B+C = 5 units.
C+A = 6 units.
-------------------
2( A+B+C) = 15 units.
A+B+C =7.5 units.
They work together 10 days, means in 10 days they have completed 75 units out of 120 units. now,
Remaining units are (120-75) = 45.
A+B+C = 7.5 (put B+C= 5 as given),
A = 2.5.
So for completing 45 units, A need (45/2.5) = 18 days.
(18)
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers