Question

A certain sum at certain rate % per annum simple interest becomes rs 2100 in 2 years and rs 2250 in 5 years. The principal and rate of interest are?

Answer 1

Principal + Interest for 5 yrs = Rs. 2250
(-) Principal + Interest for 2 yrs = (-) Rs. 2100
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Interest for 3 yrs = Rs. 150
Interest for 2 yrs = Rs. 150÷3×2
= Rs. 100
Now,
Interest for 2 yrs = Rs. 100
Amount for 2 yrs = Rs. 2100
Therefore, Principal = Rs. (2100-100) = Rs. 2000
Time = 2 yrs
Therefore, Rate of interest = Interest × 100 ÷ Principal × Time = 100×100÷2000×2 = 2.5%
Therefore, Principal = Rs. 2000
and Rate of interest = 2.5 % per annum