The difference between the compound interest and simple
The difference between the compound interest and simple interest on a certain sum for 2 years at the same rate of interest of 10% per annum is Rs. 42. The sum is-
ARs.4,200
BRs.42,000
CRs.420
DRs.4,500
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Answer is : A [Rs.4,200]
Explanation:
Let the sum be Rs.x. then S.I.= \( (\frac{x \times 10 \times 2}{100})\) = \(\frac{2x}{10}\)
C.I = \(\big[x\big(1+ \frac{10}{100}\big)^2 -x\big]\) = \(\frac{121x}{100}\)
\(\big[x \big(\frac{121}{100}\big)-x\big] =\frac{21x}{100}\)
\(=\frac{21x}{100}\)
\(\frac{21x}{100} - \frac{2x}{10} = 42 \)
=> \(\frac{x}{100} = 42\)
=> x = 4200
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