Question

What is the rate percent per annuam will a sum of mony double in8 years

Answer 1

• Let the sum be x.

  so amount  = 2 x .

• SI = 2 x - x = x.
• Time = 8 years.

Rate = (SI x 100 ) / ( P x T )

         = 100 x /8 x = 25/2 %.

Thank u.

Answer 2

$\bold{\boxed{HEY!!!}}$



Here is your answer :-



Let the rate of interest be " x p.c.p.a. " and principal be Rs.100.



Principal doubles in 8 years.



Amount = Rs.200



Simple interest = Amount - principal



= 200 - 100



= Rs.100



Simple interest = 100 .



$simple \: interest \: = \frac{principal \times rate \times time}{100} \\ \\ \\ 100 = \frac{100 \times x \times 8}{100 } \\ \\ \\ 100 = 8x \\ \\ \\ x = \frac{100}{8} \\ \\ \\ x = 12.5 \%p.a. \\ \\ \\ shortcut \: method \: \\ \\ \\ rate \: of \: interest \: = \frac{100}{time} \\ \\ \\ = \frac{100}{8} \\ \\ \\ = 12.5\%p.a$



$\bold{\boxed{Rate=12.5%\:p.a.}}$