SOLUTION: In how much time will the simple interest on a certain sum be 168rupees if it produces 21rupees as interest in 4 months at half the rate

Question 1005190: In how much time will the simple interest on a certain sum be 168rupees if it produces 21rupees as interest in 4 months at half the rate
Answer by Theo(13342) (Show Source): You can put this solution on YOUR website!
simple interest is based on the original investment only.

let x = the sum of money.

let n = the number of months.

you are given that you get 21 rupees as interest in 4 months at half the rate.

this maeans that, at full rate, you would earn 42 rupees as interest in 4 months.

since 168 is equal to 4 * 42, then you would earn 168 rupees interest in 16 months.

you could also solve as follows:

you earn 21 rupees interest in 4 months at half rate.

this means you would earn 21/4 rupees each month at half rate.

this means you would earn 42/4 rupees each month at full rate.

42/4 = 10.5 rupees each month at rull rate.

168 rupees / 10.5 rupees / month = 16 months.

still another way.

21 rupees at half rate in 4 months means 21 rupees at full rate in 2 months.

divide 168 by 21 to get 8 two month periods which is equal to 16 months.

they all point to 16 months at the number of months required to earn 168 rupees if you are earning 21 rupees in 4 months at half rate.

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