DRDO Multi tasking staff Model paper 9

Let,
Monthly salary of the man = Rs. x
Annual salary of the man = Rs. 12x
He saves 30% of his income
∴ Amount of saving in a month = 0.3x
∴ Amount of savings in a year = Rs. (0.30 × 12x) = Rs. 3.6x
Salary of 8 months = Rs. 8x
Now,
3.6x = 0.45 × 8x = 0.45 of Salary of 8 month
∴ He has to save 45% per month to save Rs. 3.6x in 8 month
New amount of saving in a month = 0.45x
∴ Percentage increase of monthly saving = [(0.45x - 0.30x)/0.30x] × 100% = ½ × 100% = 50%