Question

Qn) A person invest 10000 rupees and 15000 rupees into different schemes. After 1 year, he got 900 rupees as interest for the first amount and 1200 rupees as interest for the second amount.
1)What is the annual rate of interest in the first scheme? And in the second?
Ans:) The Rate of Interest in the first scheme = 900×100/10000=9%

The real question is how did the 100 came there in the equation?? Please explain.

Answer 1

$\underline { \blue {Case 1: }}$

$Investment \: of \: a \: person \\ first \: scheme (P) = Rs \:10000 ,\\Simple \: Interest (I) = Rs \:900, \\Time (T) = 1 \:year ,\\Let \: Rate \:of \: interest = R$

$We \: know \: that,$

$\boxed { \pink { I = \frac{PTR}{100}}}$

$\implies \frac{ I \times 100 }{PT} = R$

$\implies R = \frac{ 900 \times 100 }{ 10000 \times 1 } \\= 9\%$

Therefore.,

$\red { Rate \:of \: Interest }\green {= 9\%}$

$\underline { \blue {Case 2: }}$

$Investment \: of \: a \: person \\ Second \: scheme (P) = Rs \:15000 ,\\Simple \: Interest (I) = Rs \:1200, \\Time (T) = 1 \:year ,\\Let \: Rate \:of \: interest = R$

$We \: know \: that,$

$\boxed { \pink { I = \frac{PTR}{100}}}$

$\implies \frac{ I \times 100 }{PT} = R$

$\implies R = \frac{ 1200 \times 100 }{ 15000 \times 1 } \\= 8\%$

Therefore.,

$\red { Rate \:of \: Interest }\green {= 8\%}$

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