Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 4)
4.
A is thrice as good as workman as B and therefore is able to finish a job in 60 days less than B. Working together, they can do it in:
Answer: Option
Explanation:
Ratio of times taken by A and B = 1 : 3.
The time difference is (3 - 1) 2 days while B take 3 days and A takes 1 day.
If difference of time is 2 days, B takes 3 days.
| If difference of time is 60 days, B takes |  |
3 | x 60 |  |
= 90 days. |
| 2 |
So, A takes 30 days to do the work.
| A's 1 day's work = | 1 |
| 30 |
| B's 1 day's work = | 1 |
| 90 |
| (A + B)'s 1 day's work = | |
1 | + | 1 | |
= | 4 | = | 2 |
| 30 | 90 | 90 | 45 |
 A and B together can do the work in |
45 | = 22 | 1 | days. |
| 2 | 2 |
Discussion:
281 comments Page 24 of 29.
Balaji said:
7 years ago
Capacities of A:B=3:1.
Time taken ratio of A:B=1:3.
Difference of ratio in time is 2 = 60 days => A takes 30 days and B takes 90 days => 90/4=22 1/2.
Time taken ratio of A:B=1:3.
Difference of ratio in time is 2 = 60 days => A takes 30 days and B takes 90 days => 90/4=22 1/2.
Balaji said:
7 years ago
Capacities of A:B=3:1.
Time taken ratio of A:B=1:3.
Difference of ratio in time is 2 = 60 days => A takes 30 days and B takes 90 days => 90/4=22 1/2.
Time taken ratio of A:B=1:3.
Difference of ratio in time is 2 = 60 days => A takes 30 days and B takes 90 days => 90/4=22 1/2.
Balaji said:
7 years ago
Capacities of A:B=3:1.
Time taken ratio of A:B=1:3.
Difference of ratio in time is 2 = 60 days => A takes 30 days and B takes 90 days => 90/4=22 1/2.
Time taken ratio of A:B=1:3.
Difference of ratio in time is 2 = 60 days => A takes 30 days and B takes 90 days => 90/4=22 1/2.
Rajashekar said:
7 years ago
Shortcut of these type of problems:
A&B = Difference * 'n' times / n^2 - 1.
= 60*3/3^2-1
= 180/9-1.
= 180/8=22.5 or 22 1/2.
A&B = Difference * 'n' times / n^2 - 1.
= 60*3/3^2-1
= 180/9-1.
= 180/8=22.5 or 22 1/2.
VICKMA said:
7 years ago
Here A is thrice EFFICIENT than B.
A=1 B= 3
A takes 60days less than B to finish a work, This shows that if B takes to complete a work by "X" days. Then A will take X - 60 days to complete a piece of work.
We know that A=1.
B=3
A= X - 60
B= X (No.of day to complete a work).
Cross multiply: 3(X-60)=X => 3X-180=X,
-180=-2X => X= 90.
WORKING TOGETHER: A+B = 1/X-60 + 1/X.
We know that X = 90,
A+B = 1/90-60 + 1/90,
=1/30+1/90,
=(3+1)/90 => 4/90 => 2/ 45.
Therefore, A+B takes 45/2 days to complete a piece of work.
A+B = 22 1/2.
A=1 B= 3
A takes 60days less than B to finish a work, This shows that if B takes to complete a work by "X" days. Then A will take X - 60 days to complete a piece of work.
We know that A=1.
B=3
A= X - 60
B= X (No.of day to complete a work).
Cross multiply: 3(X-60)=X => 3X-180=X,
-180=-2X => X= 90.
WORKING TOGETHER: A+B = 1/X-60 + 1/X.
We know that X = 90,
A+B = 1/90-60 + 1/90,
=1/30+1/90,
=(3+1)/90 => 4/90 => 2/ 45.
Therefore, A+B takes 45/2 days to complete a piece of work.
A+B = 22 1/2.
SWETHA said:
7 years ago
Since A finishes the job in 60 days less, from (ii) we get: 3X - X = 60.
A=30 B=90,
A+B=1/30+1/90.
=2/45.
A and B together can do the work in 45/2=22 1/2.
A=30 B=90,
A+B=1/30+1/90.
=2/45.
A and B together can do the work in 45/2=22 1/2.
Naidu said:
7 years ago
It is a good and clear method, Thanks @Prashant.
OM PRAKASH REDDY said:
7 years ago
NO RATIO'S.
A is thrice as good as B.
This implies that if B take '' T '' days to complete the work, then A takes just ''T/3" days for same amount of the work.
Now coming to the second point in the question, A takes 60 days less than what B takes.
T/3 = T - 60.
----> T=90, ao B takes 90 days alone which implies A takes 30 days alone to complete work.
If A and B work together then no.of days required would be (1 / (1/30)+(1/90) ) which results in 22.5days.
A is thrice as good as B.
This implies that if B take '' T '' days to complete the work, then A takes just ''T/3" days for same amount of the work.
Now coming to the second point in the question, A takes 60 days less than what B takes.
T/3 = T - 60.
----> T=90, ao B takes 90 days alone which implies A takes 30 days alone to complete work.
If A and B work together then no.of days required would be (1 / (1/30)+(1/90) ) which results in 22.5days.
Shreya said:
7 years ago
@All.
This is the easiest & shortest!.
Let a be x whereas b = 3x.
So, 3x " x = 60. x = 30.
therefore a = 30, b = 90.
so when they work together-> 1/30+1/60 = 4/90 = 2/45.
Together they can do the work in 22 (1/2) days.
This is the easiest & shortest!.
Let a be x whereas b = 3x.
So, 3x " x = 60. x = 30.
therefore a = 30, b = 90.
so when they work together-> 1/30+1/60 = 4/90 = 2/45.
Together they can do the work in 22 (1/2) days.
Swarani said:
7 years ago
Your explanation is easy, thanks @Showry.
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