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:
361 comments Page 5 of 37.
Hrishi said:
6 years ago
Step 1: Work is done by A+B+C in one day can be calculated as 1/20 + 1/30 + 1/60 = 1/10.
Step 2: For the first two days only A is doing work alone so the work is done by A in two days will be 2*1/20= 1/10.
Step 3: Now total work is done in 3 days by A B & C will be = 1/10+1/10= 1/5.
Step 4: But we need a complete work to be done so we have to convert 1/5 to 1 therefore if we do 1/5 work 5 times then work will be completed (1/5 x 5=1).
Therefore 5 x 3 = 15.
Hope you will understand this solution.
Step 2: For the first two days only A is doing work alone so the work is done by A in two days will be 2*1/20= 1/10.
Step 3: Now total work is done in 3 days by A B & C will be = 1/10+1/10= 1/5.
Step 4: But we need a complete work to be done so we have to convert 1/5 to 1 therefore if we do 1/5 work 5 times then work will be completed (1/5 x 5=1).
Therefore 5 x 3 = 15.
Hope you will understand this solution.
(1)
Britney said:
6 years ago
How did we get 6/60? Anyone explain about it.
(1)
Sunil_ said:
6 years ago
A work in one day = 1/20,
B work in one day = 1/30,
C work in one day = 1/60.
As A work for 2 days and then on third day B and C do work.
Total work done in three days = A 3 days work+B 1-day work+ C one day work,
= 3/20 + 1/30 + 1/60,
= 9/60 + 2/60 + 1/60
= 12/60.
Total work is done in three days =1/5.
3 = 1/5part.
Let x days required to complete work = 1 part.
3/x = 1/5/1.
x = 3 * 5 = 15 days.
B work in one day = 1/30,
C work in one day = 1/60.
As A work for 2 days and then on third day B and C do work.
Total work done in three days = A 3 days work+B 1-day work+ C one day work,
= 3/20 + 1/30 + 1/60,
= 9/60 + 2/60 + 1/60
= 12/60.
Total work is done in three days =1/5.
3 = 1/5part.
Let x days required to complete work = 1 part.
3/x = 1/5/1.
x = 3 * 5 = 15 days.
(1)
Vijay said:
6 years ago
How we got only A done 3 days of work? Please explain it.
(1)
T.S said:
5 years ago
@Vijay
We know that the whole work done is 1. here 3 days work is 1/5.
So,
if, 1/5 work=3days.
then, 1 work= ?
Cross multiply we get ?= 3 x 5= 15days.
We know that the whole work done is 1. here 3 days work is 1/5.
So,
if, 1/5 work=3days.
then, 1 work= ?
Cross multiply we get ?= 3 x 5= 15days.
(1)
Amit bhau said:
5 years ago
3 days ---> work 1/5
x days ---> to get total work =1
Cross multiplication, then we get x = 15.
x days ---> to get total work =1
Cross multiplication, then we get x = 15.
(1)
Kiran said:
5 years ago
Hi, can anyone tell me what's wrong here?
Given,
A=20days.
B=30days.
C=60days.
I took as 60units of work by taking LCM of A, B, C.
A's one day work=3 units/day.
B's one day work=2 units/day.
A's two days work = 6 units.
B's one day work= 2 units.
C's one day work= 1 unit.
A+B+C's 3 days work = 9 units.
So, I can take A+B+C's one day work = 3 units =>9/3=3 units/day.
So, to complete 60 units of work they will take 20days =>20*3=60 units.
So, I am saying that answer is "20 days".
Correct me if I'm wrong.
Given,
A=20days.
B=30days.
C=60days.
I took as 60units of work by taking LCM of A, B, C.
A's one day work=3 units/day.
B's one day work=2 units/day.
A's two days work = 6 units.
B's one day work= 2 units.
C's one day work= 1 unit.
A+B+C's 3 days work = 9 units.
So, I can take A+B+C's one day work = 3 units =>9/3=3 units/day.
So, to complete 60 units of work they will take 20days =>20*3=60 units.
So, I am saying that answer is "20 days".
Correct me if I'm wrong.
(1)
Sairam said:
5 years ago
@Kiran.
You didn't account for A's third day of work.
A does 6 units of work in two days and another 3 units on the third day. So in total, A has done 9 units of work in 3 days.
You didn't account for A's third day of work.
A does 6 units of work in two days and another 3 units on the third day. So in total, A has done 9 units of work in 3 days.
(1)
Mythili said:
1 month ago
How 1/5 come? Please explain to me.
(1)
Chirag Lakhani said:
2 decades ago
How step 3 is make 1/10+1/10? please explain it.
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