Question

if a sum of money at simple interest becomes 4 times in 5 years, then in how many years wil it become 10 times​

Answer 1

Case 1:

Principal (P) = 1 ,

Amount (A) = 4P= 4 × 1 = 4

Simple Interest (I) = A - P

$\implies I = 4 - 1 = 3$

$Time ( T ) = 5 \: years$

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

$\implies R = \frac{ 100 \times 3}{1\times 5} \\= 60\%\: ---(1)$

Case 2:

Principal (P) = 1 ,

Rate of interest (R) = 60% , [From (1) ]

Amount (A) = 10P = 10 × 1 = 10,

Simple Interest (I) = A - P

$\implies I = 10 - 1 = 9$

$T = \frac{100\times I}{PR}$

$\implies T = \frac{ 100 \times 9}{1\times 60} \\= 15 \: years$

Therefore.,

$\pink { In \: 15 \: years \: the \: sum \: become }$

$\pink { 10 \:times }$

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