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 27 of 36.
Asanka said:
1 decade ago
If x = A worked day
{x*1/20 + x/3*(1/30+1/20)} = 1
x/20+x/60 = 1
x = 15.
{x*1/20 + x/3*(1/30+1/20)} = 1
x/20+x/60 = 1
x = 15.
Madhuri Choudhary said:
1 decade ago
I didn't understood how did they calculated the work done in 3 days. Can somebody explain me clearly?
Nitin.killekar@gmail.com said:
1 decade ago
In the last step the multiplication of 3 and 5 is for the no.of persons (3) and amount of work done (5).
Naresh said:
1 decade ago
If we add the work of b and c for 1 day we get 1/30 + 1/60=1/20.
First day = 1/20.
Second day =2/20.
Third day =4/20 // work of b & c is added 3/20 + 1/20.
Every 3 days 4/20.
For 6 days we get 8/20.
For 9 days we get 12/20.
For 12 days we get 16/20.
For 15 days we get 20/20 = 1. Job over.
First day = 1/20.
Second day =2/20.
Third day =4/20 // work of b & c is added 3/20 + 1/20.
Every 3 days 4/20.
For 6 days we get 8/20.
For 9 days we get 12/20.
For 12 days we get 16/20.
For 15 days we get 20/20 = 1. Job over.
Priti said:
1 decade ago
We have already calculate 1/5 for 3 days. Then why again multiplying by 3? please help.
Durga said:
1 decade ago
LCM of 20,30,60 is 600
A's work is 600/20
if b and c on third day then 2 days(first and second) for A and 1 day for B and c(third day)
so A's work is 600/(20*2)=600/40=15
A's work is 600/20
if b and c on third day then 2 days(first and second) for A and 1 day for B and c(third day)
so A's work is 600/(20*2)=600/40=15
Trisha said:
1 decade ago
Whole work will be done in (3 x 5) = 15 days.
I m unable to understand a last step. Explain me?
How they multiply by 5?
I m unable to understand a last step. Explain me?
How they multiply by 5?
Netra said:
1 decade ago
Please tell me why they have multiplied 3 day's work with 5.
Nirav said:
1 decade ago
@chaaya:
1/5 work done in no. of days= 3
1 work done in no. of days= ?
so it is 3/(1/5)= 3*5=15
1/5 work done in no. of days= 3
1 work done in no. of days= ?
so it is 3/(1/5)= 3*5=15
Chaaya said:
1 decade ago
Can anybody explain me why 5 is multiplied by 3 at the end??
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