Q. A and B can separately do apiece of work in 20 and 15 days respectively. They worked together for 6 days, after which B was replaced by C. If -the work was finished in next 4 days, then the number of days in which C alone could do the work will be

Option
a) 60
b) 40
c) 35
d) 30

• A and Bs one day work= 1/20+1/15=7/60
  A and Bs six day work=(7/60)*6=7/10
  remaining work=1-7/10=3/10
  A and Cs 4 day work=(A and Cs 1 day work)*4= (1/20+1/x)*4=3/10 (remaining work)
  x=40
  Cs one day work=40
• 10 years agoHelpfull: Yes(21) No(0)
• (a+b)6days work=6(1/20+1/15)=7/10
  (a+c)4days work=3/10
  (a+c)1day work=3/40
  a's 1day work=1/20
  c's1day work=3/40-1/20=1/40
  so answer is 40
• 10 years agoHelpfull: Yes(1) No(0)
• A's one day work is 1/20 days.
  B's one day work is 1/15 days.
  
  A and B is working together for 6 days,
  
  total work of A and B for 6 days is,
  (A's 1 day work x 6) + (B's 1 day work x 6)
  (1/20 x 6) + (1/15 x 6)
  (3/10) + (2/5)
  (7/10)
  
  remaining work is = 1- (7/10)
  = 3/10
  A's 4 days work is, (1/20) x 4=1/5
  C's 4 days work is , 3/10 - 1/5 = 1/10
  C's 1 day work is, (1/10) x (1/4)= 1/40
  so that C can complete a work alone in 40 days.
• 8 years agoHelpfull: Yes(1) No(0)
• b)
  1 day work of a=(1/20)
  1 day work of b= (1/15)
  then days work =6*((1/20)+(1/15))=7/10
  remaining work=(1-(7/10))=(3/10)
  a n c complete (3/10)th work in 4 days
  therefore
  4*((1/20)+(1/x))=(3/10)
  x=40
  
• 9 years agoHelpfull: Yes(0) No(0)
• Answer b) 40
  
  A actually finish the work in 20 days....
  But with B, A worked 6days and with C 4days totally 10days.
  Means A worked for half of days.
  I.e., 10days
  So A completed 50% of work...
  Then coming to B its worked for only 6days means its completed the work part of 6*1/15 =2/5
  Total work completed is A's part + B's part = 1/2 +2/5 =9/10...
  Only 1/10th part of work is pending and it is completed by C in 4 days..
  1/10th part of work done in 4days
  To finish the entire work...
  10*4 = 40
• 7 years agoHelpfull: Yes(0) No(0)