Aptitude - Time and Work - Discussion

Can we do like this?

(4/20)+(x/12)=1.
It give 9.6 and dats means 10days.

X"s one day work is 1/20.
so he worked 4 days alone which is,
4* 1/20 = 1/5 remember the Confusion avoider formula below,
(Days * single day"s work( together or alone, this case alone by X) = completed work) remember this
when we know days RHS is Completed work, if Days not known RHS is Pending work
1/5 work is completed out entire work 1
entire work - completed work = 1-1/5 = 4/5 or 80% which is pending work
pending work is 4/5 which is done by X and Y
one day's work of X and Y is 1/20 + 1/12 = 2/15 this is 1 day"s work and Inverse is the Days. If you ask WHY see X 1/20 is one day's work of X, inverse which is 20 is the number of days. Is it clear?

15/2 * 4/5= 6 days
Use this formula.

Days * single day's work ( this case by X and Y) = remaining or completed work.
Days we have to find * 2/15 = 4/5 which gives 4/5* 15/2 =6.

Now 6 days for 80% or 4/5 of the job by x and Y and 4 days for initial 1/5 or 20% of the job by x.

So, total 10 days.

4/20+x/20+x/12=1.

X=6 so total days=6+4=10days.

Clear and detailed explanation. Thank you.

Why we are calculating total time taken i.e 6+4 days. The question was asked how long did the work last?

Should it be 6 days only right? Anybody can clear my confusion?

Please explain clealrly.

Well a simple logic

1day work x =1/20
y=1/12
x first start and works upto 4 days=4*1/20
then both x and y works upto some day to completework=a(1/20+1/12)
add (4*1/20)+a(1/20+1/12)=1
we will get the days where both x and y worked=a=6

So total days to complete work =4+6=10.

How 6+4?y should we add. Please help.

Take it this way
1/5 work x does in 4 days
Remaining 4/5 is to be found
X+y does 1/20+1/12 in 1 day
Therefore x+y=2/15 w/d
Therefore 4/5 w = 2/15(w/d)/4/5(w)
We get 1/6(1/d)
Therefore 6 days
Therefore total wrk in 10 days

Harsha realy well done.