A tank fills in the sequence of 10, 20, 40, 80.... (Means 10 litres in 1 hr, 20 litres in 2nd so on.). If at the 4th hour the tank is 1/4 full .When will it be full?

• Sorry its 6
  
  At the 4th hour, it ll fill 80 litres
  80 litres is 1/4th of a tank...then the full tank can have 80 * 4 = 320 litres
  
  Given series 10, 20 ,40 ,80, (ie) each litre is double of previous litres
  
  so at the 5th hour tank filled ll be 80 * 2 = 160liters
  At the 6th hr it ll fill the full tank (ie) 160 * 2 = 320
  
  So the tank ll be full at 6th hr
  
• 10 years agoHelpfull: Yes(56) No(9)
• 10 litres-1hr
  20 litres-2hrs
  40 litres-3hrs
  80 litres-4hrs
  160litres-5hrs
  320 litres-6hrs
  
  Till 4th hour (10+20+40+80) litres of water is filled , tottal comes out to be 150 litres.. i.e 1/4 of total water..
  X*1/4=150
  x=600 litres(total capacity of the tank)
  
  If by seeing above we can make out by 5 hours(10+20+40+80+160) 310 litres will be filled , we need 290 litres to fill up the whole tank.
  
  In 6th hour 320 litres will be filled, we only need 290 out of that.
  
  320 litres=60min
  1litre=60/320 min
  290litres=(60/320)*290 mins
  Ans 5hrs 54mins
• 9 years agoHelpfull: Yes(23) No(2)
• 5 hrs. 54 min.
  
  In 4 hours tank filled(in liters)=10+20+40+80=150, which is 1/4 capacity of tank
  So the full capacity=150*4=600 liters
  The Sequence 10,20,40,80,... is a geometric series with a=10 & r=2
  Sum of Geometric Series=a[(1-r^n)/(1-r)]=600, 2^n=61, So 5
• 10 years agoHelpfull: Yes(7) No(5)
• At the 4th hour 1/4th of the tank is filled i.e, 150 litres makes 1/4 of tank(by summing 10+20+40+80)
  Then 600 litres makes full tank.
  Therefore 10,20,40,80,160,320=630 litres i.e, by 6th hour tank is full
• 10 years agoHelpfull: Yes(6) No(2)
• Ans---> after 6 hr
  
  because in 4th hr tank is 1/4 full and fills 80 litres and timing is in sequence
  so tank will be full when 80*4 = 320 liter water supply in tank..... so in 5th hr it is 160 liter and in 6th hr it is 320 liter
• 10 years agoHelpfull: Yes(5) No(6)
• 1/4 in 4th hour
  1/2 in 5th hour;as here rate of water filling is doubled
  1 in 6th hour
• 9 years agoHelpfull: Yes(4) No(0)
• 6 hours 56 minutes..
• 10 years agoHelpfull: Yes(2) No(4)
• 1 hr - 10 lit
  2 - 20
  3 - 40
  4 - 80
  
  4th hour - tank is 1/4 full
  so 10+20+40+80 = 150 litres -> 1/4 full
  
  remaining litres (3/4) for the tank to get full --> 150*3=450 litres
  
  5th hour - 160 lit
  6 - 320 lit
  
  total - 480 lit
  
  but for the tank to get full required is 450 litres - 30 litres extra
  so, b/w 5th to 6th hour- 160 lit is filled in 1 hour(60 min)
  130 lit is filled in 48 mins
  
  sol: 5 hour 48 min
• 9 years agoHelpfull: Yes(2) No(1)
• the tank fills 10 litres per hour
  At the 4th hour, it ll fill 40 litres
  40 litres is 1/4th of a tank...then the full tank can have 40 * 4 = 160litres
  
  160 litres if filled in 16 hrs
  
  so the tank ll be full at 16th hr
  
• 10 years agoHelpfull: Yes(1) No(3)
• at 1st hour 10
  at 2nd hour 20=10*2
  at 3rd hour 40=20*2
  so at each next hour it double
  it is given the question that
  at 4th hour 1/4
  so at 5th hour 1/4*2=1/2
  and at 6th hour 1/2*2=1 (i.e. full)
  so after 6 hour the tank will be full.
• 9 years agoHelpfull: Yes(1) No(0)
• for every hr tank is doubled.
  so in 4th hr-1/4
  5th hr-1/4+1/4=1/2
  6th hr-1/2+1/2=1
  for 6 hrs the tank will be filled.
• 9 years agoHelpfull: Yes(1) No(0)
• Let x be the volume of the tank.
  x/4=80,x=320 l
  At 5th hr it is 160l full,at 6th hour it is 320l full
  So,at 6th hr it is full.
• 9 years agoHelpfull: Yes(0) No(0)
• 5th hour 160
  6th hour 320
  time taken 1hour54mints
  total time taken 5hour 54mints
• 9 years agoHelpfull: Yes(0) No(1)
• tank is 1/4 full, no of 2 in 1/4 is 1/2*2=2.add 4th hour +2=6hr
• 9 years agoHelpfull: Yes(0) No(0)
• at 6 hour.
• 9 years agoHelpfull: Yes(0) No(0)