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Mathematics

Divide ₹ 15,600 into two parts such that the interest on one at 5 percent for 5 years may be equal to that on the other at 4124\dfrac{1}{2} per cent for 6 years.

Simple Interest

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Answer

Let the first part be ₹ xx and the second part be ₹ (15,600x)(15,600 - x).

Hence

P1 = ₹ xx

R1 = 5%

T1 = 5 years

S.I.=(P×R×T100)S.I.=(x×5×5100)S.I.=25x100S.I.=x4\text{S.I.} = \Big(\dfrac{P \times R \times T}{100}\Big)\\[1em] \Rightarrow \text{S.I.} = \Big(\dfrac{x \times 5 \times 5}{100}\Big)\\[1em] \Rightarrow \text{S.I.} = \dfrac{25x}{100}\\[1em] \Rightarrow \text{S.I.} = \dfrac{x}{4}\\[1em]

P2 = ₹ 15,600x15,600 - x

R2 = 412%4\dfrac{1}{2}\%

= 92%\dfrac{9}{2}\%

T2 = 6 years

S.I.=(P×R×T100)S.I.=[(15,600x)×9×62×100]S.I.=54(15,600x)200S.I.=27(15,600x)100\text{S.I.} = \Big(\dfrac{P \times R \times T}{100}\Big)\\[1em] \Rightarrow \text{S.I.} = \Big[\dfrac{(15,600 - x) \times 9 \times 6}{2 \times 100}\Big]\\[1em] \Rightarrow \text{S.I.} = \dfrac{54(15,600 - x)}{200}\\[1em] \Rightarrow \text{S.I.} = \dfrac{27(15,600 - x)}{100}\\[1em]

Both interest are equal.

x4=27(15,600x)100x4=4,21,20027x100x4+27x100=4,21,20010025x100+27x100=4,212(25x+27x)100=4,21252x100=4,212x=4,212×10052x=4,21,20052x=8,100\dfrac{x}{4} = \dfrac{27(15,600 - x)}{100}\\[1em] \Rightarrow\dfrac{x}{4} = \dfrac{4,21,200 - 27x}{100}\\[1em] \Rightarrow\dfrac{x}{4} + \dfrac{27x}{100} = \dfrac{4,21,200}{100}\\[1em] \Rightarrow\dfrac{25x}{100} + \dfrac{27x}{100} = 4,212\\[1em] \Rightarrow\dfrac{(25x + 27x)}{100} = 4,212\\[1em] \Rightarrow\dfrac{52x}{100} = 4,212\\[1em] \Rightarrow x = \dfrac{4,212\times 100}{52}\\[1em] \Rightarrow x = \dfrac{4,21,200}{52}\\[1em] \Rightarrow x = 8,100

Other amount will be ₹ (15,600 - 8,100) = ₹ 7,500.

Hence, ₹ 8,100 and ₹ 7,500 are the two parts.

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