Aptitude - Time and Work - Discussion

Here A's 2 days work = 1/20 * 2 = 1/10,
And every third day A, B and C working together,
Means A, B, C's 1 day work is A + B + C = 1/20 + 1/30 + 1/60 = 3 + 2 + 1/60 = 6/60 = 1/10
So here complete 3 days work is 1/10 + 1/10 = 2/10 =1/5.
It means 1/5 work done in 3 days.
So work remains is 1 - 1/5 = 4/5.

So here,
1/5 : 4/5 :: 3 : x
1/5 * x = 4/5 * 3
x =12.

It means 4/5 work done in 12 days,
so complete work done in,
12 + 3 = 15days.

Therefore, the answer in 15.

Work of 1 day = 1/20+1/30+1/60= 6/60= 1/10.

It means that 1/10th part of work is done in 1 day.

(It means 10% work per day).

Now every 3rd day B And C performs -ve work i.e,

Work of every 3rd day = 1/20- 1/30-1/60 = 0/60 = 0.

Days 1 2 3 4 5 6 7 8 9 10 11 12 13 14.

Work% 10+10+0+10+10+0+10+10+0+10+10+0+10+10 = 100%.

Hence work will complete in 14 days.

Note: You can consider day 15 because in day 15 the work done will 0%.

So more correct answer will 14 days.

Here first we take LCM of 20,30,60 that is 60.
After that , A work done = 60/20 = 3
Similar, B =60/30 = 2 and C = 60/60 = 1.

According to questions, A is assisted by B and C on every 3rd day.
i.e : 3 persons are Working.

Total work = A + A +(A + B + C) (Here a ,B and come together on every third day).
Total work = 3 + 3 + (3 + 2 + 1) = 12.

Now work = 60 is divided by 12 rem is 0.
Means 60/12 = 5 . We got 5 and 3 persons are working.
So that, 5 *3 = 15 days.

A's 1 day work is 1/20, B's one day work is 1/30, C's one day work is 1/60.

Given problem A is doing 2 days work alone and assisted B&C on the third day and repeats this cycle.

So, the Total work done in 3 days= (A's 2days work) + (A+B+C's 1 day work) i.e., (1/20x2) +(1/20+1/30+1/60).

(1/10) +( (3+2+1)/60) (hence 20,30,60 lcm is 60),
=> 1/10+(6/60),
=> 1/10+1/10 = 2/10=> 1/5.

Here the work done in 3 days is 1/5;
So total days required is 3x5=15.

A-20days
B-30days.
C-60days

LCM is 60
So,
A one day work 3 units (20*3)
B one day work 2 units(30*2)
C one day work 1 unit (1*60)

Then; 6 units ( both A+B+C one day work on every third day)
So A 2 days work = 3units *2 = 6 units
A+B+C on 3 Rd day = 6 units*1= 6 units
So, weget 12 units.

So 12/60 = 1/5 (A 2 days work +(A+B+C) work on a third day/total work)
So 3days * 1/5 = 15 days.
Here the answer.

Note: A alone can do its work in 20 days.

So A can do the work in 1 day is 1/20.

2nd day A can do work = (1/20)2 = 1/10.

3rd day A, B and C work together.

Therefore A's 1 day work = 1/20, B's 1 day work = 1/30, C's 1 day work = 1/60.

Together A, B and C do work in 1 day = 1/20 + 1/30 + 1/60.

= (3+2+1)/60.

= 6/60 = 1/10.

So after 3 days A's done = 1/10 + 1/10.

= 2/10 = 1/5.

= (1/5)X days = 1.

X = 5.

1/5 work = 3 days.

(1/5)X days = (3)5 days = 15 days.

Its written every 3rd day NOT First 3 days. Therefore the answer is as below:

(A+B+C)'s 1 day work = (1/20 + 1/30 + 1/60) = 1/10.

=> They all take 10 days to complete their work together.

Out of those 10 days, 3th, 6th and 9th are the 3rd days. In total B and C can help A for only 3 days.

Therefore, (A's 1 days work) + (B+C) 1 day work*3 = 1/20 + (1/30+1/60) *3 = 4/20 = 1/5.

If 1/5 is the work in 3 days, Then complete work done = 5*3 = 15.

Ans: 15 days.

Take the LCM of A, B, C which is 60.

For LCM we have to multiply A, B, C by 3,2,1 respectively, this is work done per day by each of them.

For the first 2 days, only A works so, 2*3=6.
On the 3rd day A is assisted by B&C so,total work done in one day is 6units,
Therefore, the work they have done in 3days is 6+6=12,
Total work is done =60.
Days require to complete the work by A,B, C =60 ÷ 12=5days.
Days required by A to complete work = 5*3 = 15days.

A can do 1/20 of the work per day.
B can do 1/30 of the work per day.
C can do 1/60 of the work per day.

Together, they can do 1/20 + 1/30 + 1/60 of the work per day. But since B and C only help every third day, they can do, on average, 1/20 + 1/3 (1/30 + 1/60) of the work per day.

1/20 + 1/3 (1/30 + 1/60) =
1/20 + 1/3 (3/60) =
1/20 + 1/3 (1/20) =
1/20 + 1/60 =
4/60 =
1/15.

So if they can do 1/15 of the work per day, they can finish the job in 15 days.

A can complete a work in 20 days, B can complete the same work in 30 days and with the help of C together if they complete the work in 60 days, so assume total work to be done is 60. (LCM of 20, 30, 60).

Persons A B C per 3 day.

Days- 20 30 60 12 = 6+6.

Work/day- 3 2 1 5.

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Work - 60 60 60 60.

Per 3 day ----> 12.

How many ----> 60 = (60*3)/12 = 15 days required.

Days required.