Aptitude - Time and Work - Discussion

2(1/8+1/10+1/12)+x(1/10+1/12)=1 we get x value is 2.09. required value is 11am+209=1.09pm,we taken approx value 1pm.

All the machines are started at once.
we have got the solution as 4 hrs for both machines q & r
they have started at 9 a.m.
q & r work for 4 hrs

So 9+4=13 i.e,1 p.m.

Can anyone tell

Why you put last step as 9am+4?

Already p, q, r done by 2hrs and (q&r) in 4 hrs know.

Then 2+4=6 only know.

On this step I am in confusion. Help me.

Friends

P's 2 hr work = 1/8*2=1/4
rest 3/4 work done by q&r
q+r 1hr = 1/10 + 1/12=11/60 work
3/4 work by q&r=60/11 * 3/4=4.09

The work complete time was 9a.m+4=1p.m

Thanks naveen sir.

Since machine p stops after 37 units of work is completed from 60 units of work, still (60-37=23) 23units of work is remaining. hence, 1-(37/60)= 23/60

Can some one tell me why 1-37/60 ?

Hi friends... In this problem it is having some confusion in the last step....i will explain that step in a easy way....

The work completed by q and r after closing of p machine is
23/60....
but we don't know the time...
we have to calculate it...

(q+r)'s 1 hour work = 11/60.

we can represent the above relation like this....

11/60 (portion of work)-------> 1 hour (time)

23/60 (portion of work) ------> ....? (time)


By cross multiplying the above terms we will get.

11/60 * 60/23 = 23/11

that is approximately equals to 2 ....

q and r machines took 2 hours to complete the remaining work....

i.e.,
11+2 = 1 p.m

the total 1 lakh books will be printed by 1 p.m

Hey is above told methods are applicable? to this type of problems with a small change.

Easy Solution

let total time to print the book be x
therefore
x-2/8 + x/10 + x/12= 1
Solve for x we get approx 4
so time will be 9+4=1 pm.