Given: Rate(R)% = 7.5% Time(T) = 4 years Amount = Rs. 819 Formula used: Amount = Principal(P) + Simple interest(S.I) Amount =P(1+RT/100) Calculation: According to the question, simple interest(S.I) =(P×R×T)/100 Amount = P + S.I ⇒P+PRT/100 ⇒ Amount =P(1+RT/100) ⇒819=P(1+(7.5×4)/100)< br> ⇒819=13
P
10
⇒ P = 8190/13 ⇒P=630 ∴ The amount invested was Rs. 630.Net effective rate in four year = 7.5 × 4 ⇒ 30% ⇒ 30% in fraction form = 3/10 ⇒ amount = 10 + 3 = 13 unit ⇒ 13 unit = 819 ⇒ 1unit = 63 then, ⇒ Principal = 10 unit ⇒ 10 × 63 ⇒ 630 ∴ The amount invested was Rs. 630.