Simple Interest-10th grade-3

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Mr. Todd gets interest keeping money in the bank. The interest on $600
at 6% for a certain time and that on $800 at 8% for 2 years more are
together $428. For what period are the interests calculated?

Solution: Let, $600 was lent for x years and $800 for (x + 2) years.

Interest on $600 for 1 year = $(6 * 6) = $36

So, interest on $600 for x year = $36x

Similarly, Interest on $800 for 1 year = $(8 * 8) = $64

So, interest on $600 for (x + 2) year = $64(x + 2)

By the problem, 36x + 64(x + 2) = 428

Or, 100x = 428 – 128 = 300

So, x = 3

So, $600 was lent for 3 years and $800 for 5 years.