SSC MTS 6 Aug 2019 Shift 3 Paper

Given:
Principal = Rs 480
Amount = Rs 520
Time = 20 months = 20/12 years
Concept used:
Simple interest = $\frac{\mathrm{P}\times \mathrm{R}\times \mathrm{T}\left(\mathrm{in}\mathrm{years}\right)}{100}$
Calculation:
Simple interest for 20/12 years = Amount - principal = 520 - 480
⇒ $520-480=\frac{480\times \mathrm{R}\times 20}{100\times 12}$
⇒ 40 = 8R
⇒ R = 5%
∴ The interest rate per annum is 5%.