Question

28. A sum of money at simple interest becomes four times in 24 years. The rate of
interest per annum in percentage is -
(a) 1272%
(c) 12.2%
(b) 12 %
La None of these​

Answer 1

Answer:

• Rate of interest is 12.5%.

Given:

• Amount will becomes 4 times.
• Time = 24 years.

To Find:

• Rate of interest = ?

Solution:

Let's assume:

• Let the amount be 4x.
• Let the principal be x.

As we know,

$\: \: \sf \: simple \: interest = amount - principal$

Now put on formula

$\: \: \sf \: simple \: interest = 4x - x = 3x$

Time is given = 24 years

As we know that,

$\: \: \sf \: rate \: = \frac{s.i \times 100}{p \times t}$

where,

• S.I = Simple Interest
• P = Principal
• T = Time

Now put on formula

$\: \: \sf \: rate = \frac{3 \cancel x \times 100}{ \cancel x \times 24} \\ \\ \: \: \sf \: rate = \frac{25}{2} \\ \\ \: \: \: \sf \: rate = 12.5 \: percent$

Hence,rate% is 12.5 %.

_______________________________________

Answer 2

Answer:

d) none of these

Step-by-step explanation

28 Let the original principal be x

Principal after 24 years = 4x

Therefore, Simple Interest = 4x-x =3x

Time = 24 years

ACC,

Rate of Interest = I × 100/ P × T

= 3x × 100/ 4x × 24

= 25/ 4 × 2 (AFTER CANCELLATION)

= 25/ 8

= 3•125

= 3.13 (approx.)