Tick (✓) the correct answer:
A sum of Rs 25000 was given as loan on compound interest for 3 years compounded annually at 5% per annum during the first year, 6% per annum during the second year and 8% per annum during the third year. The compound interest is
(a) Rs 5035
(b) Rs 5051
(c) Rs 5072
(d) Rs 5150
(b) Rs. 5051
Here, $A=$ Rs. $P \times\left(1+\frac{p}{100}\right) \times\left(1+\frac{q}{100}\right) \times\left(1+\frac{r}{100}\right)$
$=$ Rs. $25000 \times\left(1+\frac{5}{100}\right) \times\left(1+\frac{6}{100}\right) \times\left(1+\frac{8}{100}\right)$
$=$ Rs. $25000 \times\left(\frac{105}{100}\right) \times\left(\frac{106}{100}\right) \times\left(\frac{108}{100}\right)$
$=$ Rs. $25000 \times\left(\frac{21}{20}\right) \times\left(\frac{53}{50}\right) \times\left(\frac{27}{25}\right)$
$=$ Rs. $(21 \times 53 \times 27)$
$=$ Rs. 30051
$\therefore$ Compound interest $=$ amount $-$ principal $=$ Rs. $(30051-25000)=$ Rs. 5051