Question

1) Let us write the number of yrs for which a principal become twice of its amount having the rate of simple interest of 6¼ % per annum. ​

Answer 1

Solution :

Here , let us assume that the principal for the simple interest is Rs. x .

Now , the rate of the simple interest is 6 1/4 % per annum .

Rate :

> [ 24 + 1]/4 %

=> 25/4 % per annum .

Assume that the required number of years after the principal doubles to become twice of its amount is t years .

According to the question :

If the principal become twice itself :

=> Original Principal + SI for a certain number of years ] = 2 × Original Principal

=> Original Principal = SI for a certain number of years .

We took the original principal as Rs. x and the time as t

=> x = [ x • t • 25/4 ] / 100

=> x = [ x • t • 25/400 ]

=> x = [ x • t • 1/16 ]

=> 1 = t/16

=> t = 16 years .

Thus , the required time period is 16 years .

This is the answer .

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Answer 2

Answer:

Given :-

• A principal becomes twice of its amount having the rate of simple interest of 6 1/4% per annum.

Find Out :-

• How many years.

Formula Required :-

$\tt{\small{\boxed{\underline{\underline{\bf{Simple\: Interest\: =\: \dfrac{P \times R \times T}{100}}}}}}}$

Solution :-

⋆ Let, the principle be Rs x

⋆ Then, amount will be 2x

We know that,

S.I = Amount - Principal

⋆ Simple Interest = 2x - x = Rs x

⋆ Rate of interest = $6\dfrac{1}{4}$ = $\dfrac{25}{4}$

Hence, we get

• P = Rs x
• R % = $\dfrac{25}{4}$
• S.I = Rs x

According to the question,

➛ $\tt{x =\: \dfrac{x \times T \times 25}{100 \times 4}}$

➛ $\tt{x =\: \dfrac{x \times T \times {\cancel{25}}}{\cancel{100} \times 4}}$

➛ $\tt{x =\: \dfrac{x \times T}{16}}$

Cross multiplication,

➛ $\tt{16x = x × T}$

➛ $\tt{\dfrac{\cancel{16x}}{\cancel{x}}}$ = T

➛ $\tt{16 = T}$

➡ Time = 16 years

$\therefore$ The number of years is 16 years.