Aptitude - Time and Work - Discussion

Discussion Forum : Time and Work - General Questions (Q.No. 1)
1.
A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :

1
4

1
10

7
15

8
15

Answer: Option
Explanation:

A's 1 day's work = 1 ;
15

B's 1 day's work = 1 ;
20

(A + B)'s 1 day's work = ( 1 + 1 ) = 7 .
15 20 60

(A + B)'s 4 day's work = ( 7 x 4 ) = 7 .
60 15

Therefore, Remaining work = ( 1 - 7 ) = 8 .
15 15

Discussion:
344 comments Page 33 of 35.

Trupti said:   1 decade ago
Thanks Parthiban. I understood well.

Parthiban said:   1 decade ago
@Trupti

1-7/15 = (15-7)/15 = 8/15

I hope this will help you !

Trupti said:   1 decade ago
1-7/15 should be 6/15 please explaine how 8/15......

Rajesh Chowdary said:   1 decade ago
Explanations are good plz share any simple methods other than these

Amrinder said:   1 decade ago
4/60 is ok 4 is no of working and 60 is hours in day
cant undestand 3/60

Sagar said:   1 decade ago
@deepa
lcm of 15 and 20 is 60 so we get 7/60
understood

Sheelu said:   1 decade ago
1/15+1/20=7/60
7/60*4=8/15

Sundar said:   1 decade ago
@Vijay Kumar

1/15 + 1/20 = ?

1/15 * 4/4 = 4/60 ok.
1/20 * 3/3 = 3/60 ok.

Now,

4/60 + 3/60 = (4+3)/60 = 7/60. Thats all.

I don't know how to explain more simpler than this. Hope you can understand this. Have a nice day!

Vijay kumar said:   1 decade ago
Can you explain how 7/60 came ?

Analyser said:   1 decade ago
Since work done is 7/15....which is 7 parts out of 15.....

So obviously total work wud be 15/15......which is 1....

Hence we subtract 7/15...from 15/15 or 1..... i.e 1-7/15.


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