A sum of Rs.12,000, deposited at compound interest becomes double after 5 years. How much will it be after 20 years ?
Options:
A . Rs.1,92,000
B . Rs.1,44,000
C . Rs.1,50,000
D . Rs.1,20,000
Answer: Option A Answer: (a)A = P$(1 + R/100)^T$24000 = 12000$(1 + R/100)^5$2 = $(1 + R/100)^5$$2^4 = (1 + R/100)^20$i.e. The sum amounts to Rs.192000 after 20 years. Using Rule 11,A certain sum at C.I. becomes x times in $n_1$ year and y times in $n_2$ years then $x^{1/n_1} = y^{1/n_2}$
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