A man took a loan at simple interest at 7% in the first year with an increase of 0.5% in each subsequent year. He pays ₹ 3690 as interest after 5 yr . How much loan did he take?

Let the loan taken be ₹ P Then,
[(P x 7 x 1)/100] + [(P x 7.5 x 1)/100] + [(P x 8 x 1)/100] + [(P x 8.5 x 1)/100] + [(P x 9 x 1)/100] = ₹ 3690
⇒ P x (7 + 7.5 + 8 + 8.5 + 9)/100 = 3690
⇒ (P x 40)/100 = 3690
∴ P = (3690 x 100)/40 = ₹ 9225
Hence, the loan taken was ₹ 9225.