Water is continuously supplied from a reservoir to a locality at the steady rate of 10000 liters per hours. When delivery exceeds demand the excess water is stored in a tank. If the demand for 8 consecutive three hour periods is 10000, 10000, 45000, 25000, 40000, 15000, 60000 and 35000 liters respectively, what will be the minimum capacity required of the water tank (in thousand liters)to meet the demand and avoid any wastage?

Correct Answer: 40
We have the following table:
Period Supply DemandCalculation Excess Qty. in tank
0 - 3 hrs 30000 1000030000 - 10000 20000
3 - 6 hrs 30000 1000020000 + 30000 - 10000 40000
6 - 9 hrs 30000 4500040000 + 30000 - 45000 25000
9 - 12 hrs 30000 2500025000 + 30000 - 25000 30000
12 - 15 hrs 30000 4000030000 + 30000 - 40000 20000
15 - 18 hrs 30000 1500020000 + 30000 - 15000 35000
18 - 21 hrs 30000 6000035000 + 30000 - 60000 5000
21 - 24 hrs 30000 350005000 + 30000 - 35000 0
The excess quantity in tank at any time does not exceed 40000 litres,
Which is the required minimum capacity to avoid wastage.