3 pumps, working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day?

A.
9
B.
10
C.
11
D.
12

• 3 pump 2 days 8 hrs
  4 pump 2 days 8*3/4=6 hrs
  4 pump 1 day 6*2=12 hrs
• 13 years agoHelpfull: Yes(20) No(3)
• 3 pumps working 8 hours a day for two days.
  so the total working hours for 3 pumps together are 48 hours
  if 4 pumps are working then they must each work for 12 hours (48*12=48)
  
• 13 years agoHelpfull: Yes(12) No(3)
• in one hours empted part of tank by 3 pumps=1/16
  in one hours empted part of tank by 1 pump=1/48
  now in one hour empted part of tank by 4 pumps=1/12
  it is implies that
  1/12 part of tank empted in =1 hour
  1 (1=whole part ) or tank will be empted in=(1*1)/(1/12)=12
  
  answer==12 hours
  D
• 13 years agoHelpfull: Yes(6) No(1)
• p1*h1*d1=p2*h2*d2;
  3*8*2=h*4*1;
  h=12 ans...
• 9 years agoHelpfull: Yes(4) No(0)
• ans.D
  3 pumps 8 hrs a day for 2 days working at rate r to complete wrk w.
  3*8*r*2=w.....(1)
  4 pumps x hrs a day for 1 day working at rate r completes wrk w.
  4*r*x*1=w.....(2)
  (1)/(2)
  x=12
  
• 13 years agoHelpfull: Yes(2) No(2)
• simple ratio proportion question :
  x hrs = 8 X 3/4 X 2/1
  
  ( in 3/4, 3 is in numerator as the no of pumps has decreased so hours taken will be less)
  (in 2/1, 2 is in numerator and 1 is in denominator as no of day is increased so hours taken will be greater)
• 9 years agoHelpfull: Yes(0) No(0)