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 5 of 36.
Samiksha koli said:
6 years ago
@All.
I couldn't get this. Because A is assisted by B & C on the third day only.
So, A B C will together work for first two days. And for last day A will work alone because he is assisted by B & C for third day. So total work of three days Will be A+B+C=1/10 for 2 days it will be 1/5 and A's last day's work will be 1/20.
So, the total work of three days will be1/4. So total work has to be done in 3*4=12 days.
Correct me, if I am wrong.
I couldn't get this. Because A is assisted by B & C on the third day only.
So, A B C will together work for first two days. And for last day A will work alone because he is assisted by B & C for third day. So total work of three days Will be A+B+C=1/10 for 2 days it will be 1/5 and A's last day's work will be 1/20.
So, the total work of three days will be1/4. So total work has to be done in 3*4=12 days.
Correct me, if I am wrong.
Mohosin said:
1 decade ago
We can solve it in this way also:
In 1 day, A alone can do 1/20th f the work,
So, in 2 days A can do (1/20 * 2)= 1/10th f the work
On 3rd day A,B and C together do= (1/20 + 1/30 + 1/60)= 6/60= 1/10
___________________________________________________________
Now, after 3 days, total work done= (1/10 + 1/10)=2/10=1/5
so, in 3 days they can complete 1/5th of the work.
so, for completing the whole work, they need (5*3) days= 15days
In 1 day, A alone can do 1/20th f the work,
So, in 2 days A can do (1/20 * 2)= 1/10th f the work
On 3rd day A,B and C together do= (1/20 + 1/30 + 1/60)= 6/60= 1/10
___________________________________________________________
Now, after 3 days, total work done= (1/10 + 1/10)=2/10=1/5
so, in 3 days they can complete 1/5th of the work.
so, for completing the whole work, they need (5*3) days= 15days
Ganesh said:
10 years ago
Total work = 60 units (lcm of 20, 30 and 60).
A completes work in 20 days. It means 3 units a day.
B completes work In 30 days. It means 2 units a day.
C completes work in 60 days. It means 1 unit a day.
A is working 2 days alone. It means 3+3 = 6 units is completed.
On third day B and C helping A.
It means on third day 3 +2+1 = 6 units of work is completed.
It means for 3 days 12 units of work is completed.
For 60 units?
60*3/12 = 15.
A completes work in 20 days. It means 3 units a day.
B completes work In 30 days. It means 2 units a day.
C completes work in 60 days. It means 1 unit a day.
A is working 2 days alone. It means 3+3 = 6 units is completed.
On third day B and C helping A.
It means on third day 3 +2+1 = 6 units of work is completed.
It means for 3 days 12 units of work is completed.
For 60 units?
60*3/12 = 15.
Prem K said:
7 years ago
A's 1 day's work is 1/20.
A's 3 day's work is 3/20.
(B+C)'s 1 day's work is 1/30+1/60 = 1/20.
B and C will work on every third day means A will work three days and B and C will work for 1 day.
(A+B+C)'s 3 day's work = A's 3 day's work + (B+C)'s 1 day's work,
= 3/20 + 1/20,
= 1/5.
3 day's work is 1/5 then, whole work will be done in (3*5) = 15 days.
A's 3 day's work is 3/20.
(B+C)'s 1 day's work is 1/30+1/60 = 1/20.
B and C will work on every third day means A will work three days and B and C will work for 1 day.
(A+B+C)'s 3 day's work = A's 3 day's work + (B+C)'s 1 day's work,
= 3/20 + 1/20,
= 1/5.
3 day's work is 1/5 then, whole work will be done in (3*5) = 15 days.
Ravi said:
6 years ago
First, we took lcm of all 3 that is A, B and C that is 60. On the basis of this A's efficiency is 3, B's efficiency is 2 and C's 1. So first 2 days A will do the work that is 3x2=6. Third-day work will be 6 as all three are doing the work. So 3 day's work will be 12. On the basis of the unitary method in every 3 day, they are doing 12 work so 3 day's efficiency will be 4unit. So, total work that is 60 divide by 4= 15.
Saraswati said:
1 decade ago
Another method to solve this problem:
A can do the work in 1 day = 1/20.
A can do the work in 2 days = 1/20*2 = 1/10.
B+C can do the work in 1 day = 1/30+1/60 = 1/20.
B+C can do the work in 3 days = 1/20*3 = 3/20.
A is assisted by B and C on every third day.
So that 1/20+3/20 = 1/5 (1 days work of A+3 days work of B and C).
Now, 1/5 work is done in 3 days,
Therefore whole work will be done in (3*5) = 15 days.
A can do the work in 1 day = 1/20.
A can do the work in 2 days = 1/20*2 = 1/10.
B+C can do the work in 1 day = 1/30+1/60 = 1/20.
B+C can do the work in 3 days = 1/20*3 = 3/20.
A is assisted by B and C on every third day.
So that 1/20+3/20 = 1/5 (1 days work of A+3 days work of B and C).
Now, 1/5 work is done in 3 days,
Therefore whole work will be done in (3*5) = 15 days.
Pooja Kulkarni said:
8 years ago
It can be done in an easier way than the given solution:
Let the number of days required = x.
So basically, B will contribute (1/3)rd of its work in 30 days and C will contribute (1/3)rd of its work in 60 days.
Work by A in one day: 1/20.
Work by B in one day: 1/30.
Work by C in one day: 1/60.
So total work can be easily calculated as:
(x/20) + (1/3)*(x/30) + (1/3)*(x/60) = 1.
So, 12x = 180,
And thus x = 15 days.
Let the number of days required = x.
So basically, B will contribute (1/3)rd of its work in 30 days and C will contribute (1/3)rd of its work in 60 days.
Work by A in one day: 1/20.
Work by B in one day: 1/30.
Work by C in one day: 1/60.
So total work can be easily calculated as:
(x/20) + (1/3)*(x/30) + (1/3)*(x/60) = 1.
So, 12x = 180,
And thus x = 15 days.
Raman said:
1 decade ago
"A" can complete work in 20 days.
A's 1 day work is 1/20.
A's 2 days work is 2/20.
A's first day + A's second day + (A + B + C).
=> 1/20+1/20/+ (1/20+1/30+1/60).
=>2/20+ (1/20+1/30+1/60).
=>2/20+1/10 = 1/5.
So 3 days work = 1/5 convert it to one day work.
3/1/5 = 5/1*3 = 5*3 = 15 days.
Other way:
= 1/5 in three days we want to finish work.
= 1/5 + 1/5 + 1/5 + 1/5 + 1/5 = 5/5 = work finished.
A's 1 day work is 1/20.
A's 2 days work is 2/20.
A's first day + A's second day + (A + B + C).
=> 1/20+1/20/+ (1/20+1/30+1/60).
=>2/20+ (1/20+1/30+1/60).
=>2/20+1/10 = 1/5.
So 3 days work = 1/5 convert it to one day work.
3/1/5 = 5/1*3 = 5*3 = 15 days.
Other way:
= 1/5 in three days we want to finish work.
= 1/5 + 1/5 + 1/5 + 1/5 + 1/5 = 5/5 = work finished.
Eliz said:
1 decade ago
Day1: A works alone = 1/20.
Day2: Again, A works alone = 1/20.
Day3: Includes work of A, B and C = 1/20+1/30+1/60.
=>6/60.
=>1/10.
NOW, work in all 3 days = 1/20 + 1/20+ 1/10.
=>1/5.
Work in 1 day =1/(3*5).
=>1/15.
Taking reciprocal now will give us the no: of days.
i.e., 15.
Day2: Again, A works alone = 1/20.
Day3: Includes work of A, B and C = 1/20+1/30+1/60.
=>6/60.
=>1/10.
NOW, work in all 3 days = 1/20 + 1/20+ 1/10.
=>1/5.
Work in 1 day =1/(3*5).
=>1/15.
Taking reciprocal now will give us the no: of days.
i.e., 15.
Poonam said:
5 years ago
Here is a solution:
Efficiency A = 3 , B = 2, C = 1 and A+B+C = 6.
Now,
Work done in format ie A can do a work in 2day and next 1day with B&c .
So.
Eff * time = work.
A = 3 * 2 = 6.
A + B + C = 6 * 1 = 6.
Means work done in 3 days is 6 + 6 = 12 work.
Days -------- work
3 -------- 12
? ------- 60 (total work)
Days =(60*3) / 12.
The answer is = 15 days.
Efficiency A = 3 , B = 2, C = 1 and A+B+C = 6.
Now,
Work done in format ie A can do a work in 2day and next 1day with B&c .
So.
Eff * time = work.
A = 3 * 2 = 6.
A + B + C = 6 * 1 = 6.
Means work done in 3 days is 6 + 6 = 12 work.
Days -------- work
3 -------- 12
? ------- 60 (total work)
Days =(60*3) / 12.
The answer is = 15 days.
(1)
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers