Question

plz answer these questions

Answer 1

15. a tap can fill a cistern in 8 hours.
part of cistern in one hours = 1/8
a tap can empty the cistern in 16 hours.
Part of cistern emptied in one hours = - 1/16 ( negative sign shows that the cistern in being drained)
part of cistern filled in one hours = 1/8 - 1/16 =1/16
time required to fill the cistern 16 hours


16. a pump can fill a tank in 2 hours.
part of the tank filled the pump in one hours = 1/2
suppose the leak empties a full tank filled in one hours = 1/2- 1/x =3/7 ( given)
1/x=1/2-3/7=7-6/14
= 1/14
x = 14 hours


17. part of the tank filled by the first pipe in one hour = 1/10
part of the tank filled by the second pipe in one hour = 1/12
part of the tank filled by the third pipe in one hour = -1/20
part of the tank filled by three pipes in one hour = 1/10 + 1/12 -1/20 = 2/15
total time taken to fill the tank = 15/2 hours = 7 hours 30 minutes