Rajiv gets an increment of 25% every year in his salary, with the increase in salary his expenditure also increases by 10% every year. In the present year Rajiv saves Rs. 99825. What was his savings 3 years back if the savings and expenditure is equal this year and an additional Rs. 350 is kept for donation this year?
Rajiv gets an increment of 25% every year in his salary, with the increase in salary his expenditure also increases by 10% every year. In the present year Rajiv saves Rs. 99825. What was his savings 3 years back if the savings and expenditure is equal this year and an additional Rs. 350 is kept for donation this year? Correct Answer Rs. 27400
Given:
Salary increases by 25% every year
Expenditure increases by 10% every year
Expenditure is equal to savings in the present year that is Rs. 99825
Rs. 350 kept for donation other than savings and expenditure
Concept:
Salary is the sum of expenditure and savings and donations
Formula:
F = S(1 + i/100)n
Where, F = final amount after n years, S = present amount, i = increment percent, n = number of years
Savings = income – expenditure
Calculation:
Let salary 3 years back was x
Present salary = x(1 + 25/100)3
Let expenditure 3 years back was y
Present expenditure = y(1 + 10/100)3
y(1 + 10/100)3 = 99825
⇒ y(110/100)3 = 99825
⇒ y(11/10)3 = 99825
⇒ 1.331y = 99825
⇒ y = 75000
Present salary = Rs. (99825 + 99825 + 350) = Rs. 200000
x(1 + 25/100)3 = 200000
⇒ x(125/100)3 = 200000
⇒ x × 1.253 = 200000
⇒ x = 102400
Savings 3 years back = Rs. (102400 – 75000) = Rs. 27400
∴ Savings 3 years back is Rs. 27400