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Aptitude - Time and Work - Discussion

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"I never see what has been done; I only see what remains to be done."
- Marie Curie
26.

A and B can do a work in 8 days, B and C can do the same work in 12 days. A, B and C together can finish it in 6 days. A and C together will do it in :

 [A]. 4 days [B]. 6 days [C]. 8 days [D]. 12 days

Explanation:

 (A + B + C)'s 1 day's work = 1 ; 6

 (A + B)'s 1 day's work = 1 ; 8

 (B + C)'s 1 day's work = 1 . 12

(A + C)'s 1 day's work
 = 2 x 1 - 1 + 1 6 8 12
 = 1 - 5 3 24
 = 3 24
 = 1 . 8

So, A and C together will do the work in 8 days.

 Nandakumar said: (Tue, Jan 18, 2011 08:11:34 AM) How can i take 2*1/8-(1/8+1/12)?

 Bhanu said: (Thu, Jan 27, 2011 06:52:43 AM) (A + B + C)'s 1 day's work = 1/6 (A + B)'s 1 day's work = 1/8 (B + C)'s 1 day's work = 1/12 so c's 1 day's work=1/6-1/8=1/24 and a's 1 day's work=1/6-1/12=1/12 and b's 1 day work=1/6(1/24+1/12)=1/4 so a and c 1'day work=1/12+1/24=1/8

 Akiii said: (Sun, Mar 27, 2011 12:02:53 PM) Good explanation.

 Azuu said: (Thu, Aug 11, 2011 10:20:57 AM) How to take lcm of 1/8+1/12 ?

 Sabarimani said: (Mon, Aug 15, 2011 06:17:54 PM) Is b's 1day work=1/6-(1/24+1/12)?

 Gulshan said: (Sat, Oct 22, 2011 02:58:23 PM) 24 is lcm of 8 & 12

 Kavitha said: (Mon, Feb 20, 2012 12:52:19 PM) Why did you take 1/6 (1/12+1/24) ?

 Anishkumar said: (Wed, Mar 7, 2012 09:48:55 PM) Assume A+C as x so now 2(A+B+C)=1/8+1/12+1/x 2(1/6) =5/24+1/x finally x =8

 Parveen Verma said: (Tue, Mar 20, 2012 08:30:24 PM) (A+B+C)=1/6 A's one day work work= (A+B+C)-(B+C)= 1/6-1/12 =1/12 C's one day work work= (A+B+C)-(A+B)= 1/6-1/8= 1/24 (A+C)'s one day work= 1/12+1/24= 1/8 so the work will be completed in 8 days

 Sujeet said: (Fri, Apr 20, 2012 12:52:41 AM) Why 2 is multiplied by 1/6.

 Basu said: (Wed, Sep 5, 2012 12:01:48 PM) How its come on 1/6-1/2=1/12 1/6-1/8= 1/24 1/12+1/24= 1/8

 Nice Dreamer said: (Fri, Sep 21, 2012 01:34:15 PM) Why 2 is multiplied with 1/6 ? please explain any one.

 Nik said: (Sat, Sep 22, 2012 07:37:19 PM) 1 day's work of(A+B)=1/8 1 day's work of (B+C)=1/12 lets take 1 day's work of (A+C)=1/x adding the above we get 2(A+B+C)=1/8+1/12+1/X dr4 2(1/6)=(1/8)+(1/12)+(1/x) 1/x=(2/6)-(1/8)-(1/12) 1/x=1/8

 Dhanshree said: (Tue, Mar 19, 2013 04:04:28 PM) (A+B) work is = 1/8. (B+C)work is = 1/12. (A+B+C)work is = 1/6. Only A's work = 1/6-1/12 = 1/12. Only C's work=1/6-1/8 = 1/24. Hence (A+C)'s complete work is = (1/12+1/24) = 1/8. (A+C)'s complete work in 8 day.

 Monu said: (Sat, Apr 27, 2013 01:34:02 PM) Why can't we simply subtract A+B's 1 day work from B+C's 1 day work to get A+C's 1 day work?

 Sk.Gopinath said: (Mon, May 20, 2013 06:39:08 PM) A+B+C = 1/6; A+B = 1/8; B+C = 1/12; C's 1day work is =>1/6 - 1/8 =>1/24. A's 1day work is =>1/6 - 1/12 =>1/8. A+C 's 1day's work =>1/24 + 1/12. = 1/8 = 8 days.