Madhya Pradesh Police Exam Model Paper 10

Given:
Rate(R)% = 7.5%
Time(T) = 4 years
Amount = Rs. 819
Formula used:
Amount = Principal(P) + Simple interest(S.I)
Amount $=\mathit{P}\left(1+\mathit{R}\mathit{T}/100\right)$
Calculation:
According to the question,
simple interest(S.I) $=\left(\mathit{P}\times \mathit{R}\times \mathit{T}\right)/100$
Amount = P + S.I
$\Rightarrow \mathit{P}+\mathit{P}\mathit{R}\mathit{T}/100$
⇒ Amount $=\mathit{P}\left(1+\mathit{R}\mathit{T}/100\right)$
br> $\Rightarrow 819=13\frac{\mathit{P}}{10}$
⇒ P = 8190/13
$\Rightarrow \mathit{P}=630$
∴ 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.