A person invested some amount at 15% simple interest and some at 20% simple interest. He received yearly interest of Rs.250.50. But if he had interchanged the amount invested he would have received Rs.10 more as interest. How much did he invest at 15% simple interest?

830

Let the amount invested at 15% = x

Let the amount invested at 20% = y

ATQ,

15x + 20y = 250.5

15y + 20x = 260.5

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By equating,

45x + 60y = 751.5

60y + 80x = 1042

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x = 8.3

100x = 830