Question

A sum of money amounts to +52,080 in 2 years and to 77,280 in 7 years, at simple interest. Find the
sum and rate percentage of interest.​

Answer 1

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Principle + Interest for 7 years = ₹ 77280

Principle + Interest for 2 years = ₹ 52080

Find the Interest for 5 years :-

Interest for 5 years = ₹ (77280 - 52080) = ₹ 25200

Find the Interest for 2 years :-

Interest for 1 years = ₹ (25200/5) = ₹ 5040

Interest for 2 years = ₹ (5040 × 2) = ₹ 10080

Find the principle :-

Principle = 52080 - Interest for 2 years

= ₹ (52080 - 10080 )

= ₹ 42000

Find the rate percent :-

Rate = (100 × Interest for 2 years)/(principal × time) %

= (100 × 10080)/(42000 × 2) %

= 1008000/84000 %

= 12 %

Hence,

Principle = ₹ 42000

Rate percent = 12 %