If working efficiency of pipes a and B is in the ratio of 5:2. If the total volume of the water to be filled is 70 litres. Find in how many days pipe A will fill the tank?

14 days

                          A        :         B

 Efficiency   →     5         :         2

Time          →     2         :         5

Total amount = 2 × 5 = 10

               10 → 70

                 1 → 7

Time taken by A = 7 × 2 = 14 days