Question

Atr% per annum a sum doubles after 10 years in simple interest. The
rate of interest per annum is​

Answer 1

Answer :-

Let principal be x

Amount = 2x

→ Simple interest = Amount - Principal

→ SI = 2x - x

→ SI = x

Now, we have :-

• SI = x
• P = x
• t = 10 years

We know that,

SI = P × R × T / 100

Substituting the values :-

→ x = x × r × 10 / 100

→ x = 10xr / 100

→ x / x = 10 r / 100

→ 1 = r / 10

→ r = 10

Rate of interest per annum = 10%

Answer 2

$\sf \: {Answer :-}$

☑ 10% is the answer!!

Solution :-

• Let principal be x
• So Amount = 2x

$\fbox{→ Simple interest = Amount - Principal}$

→ Simple interest = 2x - x

→ Simple interest = x

$\implies\bold{SI = \frac{P × R × T }{100} }$

Substituting the values :-

$\implies$ x = x × r × 10 ÷ 100

$\implies$ x = 10xr ÷ 100

$\implies$ x ÷ x = 10 r ÷ 100

$\implies$1 = r ÷ 10

$\implies$r = 10

Rate of interest per annum = 10%