Question
A person’s monthly income increases by 20% and his
monthly expenditure increases by 10%. If his savings increase from Rs 5000 to Rs 8000, then his original monthly income was:Solution
Let original income = I and original expenditure = E. Original savings: I − E = 5000 ...(1) After increase: New income = 120/100 × I = 6I/5 New expenditure = 110/100 × E = 11E/10 New savings: (6I/5) − (11E/10) = 8000 ...(2) Multiply (1) by 11/10: (11I/10) − (11E/10) = 5500 ...(3) Now subtract (3) from (2): (6I/5 − 11I/10) = 8000 − 5500 (12I/10 − 11I/10) = 2500 I/10 = 2500 I = 25000
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