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:
283 comments Page 18 of 29.
Raj said:
1 decade ago
Easy lets assume A works total days = X.
So A one day work = 1/X.
B is working 3 times less than A.
So Total days of B is = 3X.
So B Works one day = 1/3X.
Different between total days of B and A is 60.
So 3X-X = 60.
2X = 60.
X = 30.
Now normal maths. Replace X with numbers. You will get answer.
So 1/30-1/90 = 22.5.
So A one day work = 1/X.
B is working 3 times less than A.
So Total days of B is = 3X.
So B Works one day = 1/3X.
Different between total days of B and A is 60.
So 3X-X = 60.
2X = 60.
X = 30.
Now normal maths. Replace X with numbers. You will get answer.
So 1/30-1/90 = 22.5.
Sachin said:
1 decade ago
Its very simple.
Suppose B's done work = X day.
Then A's done work = (X-60) day.
Efficiency ratio is.
A : B = 1:3.
(X-60) : (X) = 1:3.
X = 90.
So A's take days = 30.
B's take day = 90.
A's 1 day work = 1/30.
B's 1 day work = 1/90.
(A+B) s 1day work = 1/30 + 1/90 = 2/45.
So together they will take = 45/2.
Suppose B's done work = X day.
Then A's done work = (X-60) day.
Efficiency ratio is.
A : B = 1:3.
(X-60) : (X) = 1:3.
X = 90.
So A's take days = 30.
B's take day = 90.
A's 1 day work = 1/30.
B's 1 day work = 1/90.
(A+B) s 1day work = 1/30 + 1/90 = 2/45.
So together they will take = 45/2.
Govardhan reddy said:
1 decade ago
Why were their difference between days? Please explain to me.
AaA said:
1 decade ago
Is there a fixed formula for this?
Ankita said:
1 decade ago
Suppose A takes x days.
Then, B will take 3x days.
From question, 3x-x = 60.
=> x = 30.
=> A takes 30 days and B takes 90 days.
Together they will take = 30*90/30+90.
= 30*90/120.
= 90/4.
= 22.5 or 22 1/2 days (ans).
Then, B will take 3x days.
From question, 3x-x = 60.
=> x = 30.
=> A takes 30 days and B takes 90 days.
Together they will take = 30*90/30+90.
= 30*90/120.
= 90/4.
= 22.5 or 22 1/2 days (ans).
Priya said:
1 decade ago
No need to do all that simply guess numbers 30 & 90 which is satisfying this then without using pen we can get answer 22.5 days.
Ankita said:
1 decade ago
If B takes y days , A takes (y-60 ) days. Now , their efficiency are A:B = 3x : x.
So total unit of work is 3x*(y- 60 ) man days = x*y man days.
Calculating this we get y = 90. So if B worked for 90 days, A worked for 30 days.
Hence 1/30 + 1/90 = 22 1/2 days :).
So total unit of work is 3x*(y- 60 ) man days = x*y man days.
Calculating this we get y = 90. So if B worked for 90 days, A worked for 30 days.
Hence 1/30 + 1/90 = 22 1/2 days :).
Prakash said:
1 decade ago
But there is not given difference in question they given A finish work in 60 day?
Sumit said:
1 decade ago
If difference of time is 60 days, B takes 3/2 x 60 = 90 days.
Please explain this statement.
Please explain this statement.
Mohit jain said:
1 decade ago
Let,
A takes = x days.
B will take = 3x days.
Difference 3x-x = 60.
So 2x = 60.
x = 30 days.
Thus A can do it in 30 days and B in 90 days.
A takes = x days.
B will take = 3x days.
Difference 3x-x = 60.
So 2x = 60.
x = 30 days.
Thus A can do it in 30 days and B in 90 days.
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