Question
A certain sum amounts to ₹22,494 in 7 years at x% per
annum on simple interest. If the rate of simple interest per annum had been (x + 4) %, the amount payable after 7 years would have been ₹25,9120. Find the sum invested.Solution
Rate of interest per annum in 1st case =x% Rate of interest per annum in 2nd case =(x+4) Let the Sum =100y. ATQ- 
100y+6xy+28y=25920 128y+6xy =25920…put the value of eq (1) 128y+22494-100y=25920 28y=3426 Y=122.35 Total Sum =100×122.35 =12235.
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