Aptitude - Time and Work - Discussion

Hi, I'm not getting the below logic in quotes

" Complete 3 days work is 1/10 + 1/10 = 2/10 =1/5"

Shouldn't that be [ (A's ist day)+ (A's 2nd day) + (A+B+C combined on 3rd day)]?

ie = 1/20 + 1/10 + 1/10?

Please correct me if I am wrong.

For whole work take lcm of 20,30 and 60 ie 60 so whole work is 60.
A alone work = 60/20 = 3w/d.
B=2w/d.
C=1w/d.
A+b+c= 6w/d.
A work 3 /day so 60/3=10 days.
It means A alone work 10 days and ie,
10*3(A per day work)= 30.
Remaining work 60-30=30.
So remaining 30 work done by;
A+B+C= 30/6(pr day work)= 5 days,
So total days 10(alone A)+ 5(A+B+C)=15 days.

Take whole work is 1.B and C assists A only 3rd day.
So A"s two day work is 1/10.
On 3rd day total work is done is 1/5.

That means 1/5 work done taken in 3rd day. So whole work(1) is done in 15 days.

Suppose B and C are helping a, = b 1/30 + c 1/60 + a 1/20.

But B and C are helping only on third day so( b+c / 3)+a = (1/30+1/60 =3/60 = 1/20/3=1/60)+ 1/20= 1/20+1/60=4/60=1/15 = 15.

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.

How did we get that 1/10+1/10 ? Can anyone help me?

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.

Why here they take 2?

I'm finding difficulty in understanding the question. How to analyze the question? Please help me out.

Here, first of all, we have to find the total work.
So for this, L.C.M of 20 30 60 = 60,
a's b's c's one day work =3 2 1 (one day work)
Now a's 2days work = 6.
b's, c,s one day's woks = 2.
+1= 3.
So three days work 3 + 3 + 3 + 3 = 12.
3 days = 12
3*5 =15 days, 12 * 5 = 60.