Aptitude - Time and Work - Discussion
Discussion Forum : Time and Work - General Questions (Q.No. 3)
3.
A, B and C can do a piece of work in 20, 30 and 60 days respectively. In how many days can A do the work if he is assisted by B and C on every third day?
Answer: Option
Explanation:
| A's 2 day's work = |  |
1 | x 2 |  |
= | 1 | . |
| 20 | 10 |
| (A + B + C)'s 1 day's work = | |
1 | + | 1 | + | 1 | |
= | 6 | = | 1 | . |
| 20 | 30 | 60 | 60 | 10 |
| Work done in 3 days = | |
1 | + | 1 | |
= | 1 | . |
| 10 | 10 | 5 |
| Now, | 1 | work is done in 3 days. |
| 5 |
Whole work will be done in (3 x 5) = 15 days.
Discussion:
357 comments Page 28 of 36.
Arun said:
1 decade ago
Can you explain the 3rd step please?
Karthikeyan said:
1 decade ago
Please explain me the lcm method for this problem.
Narayana said:
1 decade ago
A work in 2 Days = 1/20*2 = 1/10.
After 3rd day add in B, C. So A, B, C work in 1 day.
= 1/20+1/30+1/60 = 1/10.
2days + 1 day = 1/10+1/10 => 1/5.
Work completed = 1/5*3 = 15 days.
After 3rd day add in B, C. So A, B, C work in 1 day.
= 1/20+1/30+1/60 = 1/10.
2days + 1 day = 1/10+1/10 => 1/5.
Work completed = 1/5*3 = 15 days.
Vinay vidhani said:
1 decade ago
Please tell me some one where I'm doing mistake.
Hear A can do a work in 20 days B-30 days and C doing in 60 days.
A's 3 day work is 1/20*3.
B's work will be on 3rd day is 1/90 and C's - 1/180 they work together then answer is coming 6 days please tell about that's solution soon please.
Hear A can do a work in 20 days B-30 days and C doing in 60 days.
A's 3 day work is 1/20*3.
B's work will be on 3rd day is 1/90 and C's - 1/180 they work together then answer is coming 6 days please tell about that's solution soon please.
Shakti said:
1 decade ago
Last step. 1/5th of work completed in 3 days.
We have to find 1 or whole work can completed in how many days.
1/5th work= 3 days.
1 work= 3/ (1/5) = 3*5= 15 days.
We have to find 1 or whole work can completed in how many days.
1/5th work= 3 days.
1 work= 3/ (1/5) = 3*5= 15 days.
Tuhin said:
1 decade ago
EASY WAY FOR THIS QUESTION :
Let total no. of days be= N
Work done by A,B,C respectively per day are :1/20,1/30,1/60
As B and C join every third day there work done by them :(N/3)/30 and (N/3)/60 respectively.
And for A : N/20
Total work=
N/20+(N/3)/30+(N/3)/60=1
We get N as 15
Let total no. of days be= N
Work done by A,B,C respectively per day are :1/20,1/30,1/60
As B and C join every third day there work done by them :(N/3)/30 and (N/3)/60 respectively.
And for A : N/20
Total work=
N/20+(N/3)/30+(N/3)/60=1
We get N as 15
Kumar said:
1 decade ago
@Preethi
Finally we got the answer 1/5->work completed in 3 days clear upto here.Coming to your doubt we have to know the full work completed in no of days 1/5th work == 3days=1/5th work Just make above Rhs as 1 Full work == 3*? =1/5*5
== 3*5 =1/5*5
1 Full work in 15 days == 15 =1
Hope your doubt is cleared.
Finally we got the answer 1/5->work completed in 3 days clear upto here.Coming to your doubt we have to know the full work completed in no of days 1/5th work == 3days=1/5th work Just make above Rhs as 1 Full work == 3*? =1/5*5
== 3*5 =1/5*5
1 Full work in 15 days == 15 =1
Hope your doubt is cleared.
Anonymous said:
1 decade ago
Why do you need to find A's work in 2 days?
Kranthi said:
1 decade ago
A's 1 day work = 1/20
B every 3 days = 3/30
C also every 3 days = 3/60
Total work = 1/20+3/30+3/60
= 3+6+3/60 = 12/60 =1/5
3*5 days=full work completed
15
Is it correct way
B every 3 days = 3/30
C also every 3 days = 3/60
Total work = 1/20+3/30+3/60
= 3+6+3/60 = 12/60 =1/5
3*5 days=full work completed
15
Is it correct way
Karthik said:
1 decade ago
@Preethi.
3*5 because 1/5*5 gives you 1 which means the work has been completed. So 1/5 is derived for work done in 3 days. Understood ah.
3*5 because 1/5*5 gives you 1 which means the work has been completed. So 1/5 is derived for work done in 3 days. Understood ah.
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