Delhi Police Constable Exam Model Paper 1

GIVEN:
Rate of interest is 6% per annum for the first 2 years, 8% per annum for the next 2 years and 10% per annum for the last 2 years.
Principal = Rs. 40000
CONCEPT:
Simple interest concept.
Cumulative rate if the rate of interest is ‘ ${\mathit{R}}_1$ ’ for ‘ ${\mathit{T}}_1$ ’ years and ‘ ${\mathit{R}}_2$ ’ for ‘ ${\mathit{T}}_2$ ’ years = ${\mathit{R}}_1{\mathit{T}}_1$ $+{\mathit{R}}_2{\mathit{T}}_2$
FORMULA USED:
SI = PRT/100
Where P = Principal, R = rate of interest, T = Time
CALCULATION:
Cumulative rate = $6\times 2+8\times 2+10\times 2=48\%$
Principal = Rs. 40000
So,
SI = [40000 × 48]/100
⇒ SI = 19200
Hence,
Total interest earned = Rs. 19200