Question

0)
At what rate of interest a certain sum will be doubled in 8 years?​

Answer 1

Answer :

• At 12.5% rate of interest sum will be doubled in 8 years!!

⠀⠀━━━━━━━━━━━━

Given :

• Time = T = 8 years

Solution :

Let us assume that,

• Principal = P

• SI = P

Also,

We know that,

• SI = PTR / 100

By using the above formula,

$\sf \dashrightarrow \: \: \: Rate = \dfrac{100 \times P }{8 \times P} \\ \\ \\ \sf \dashrightarrow \: \: \: \dfrac{100}{8} \\ \\ \\ \sf \dashrightarrow \: \: \:{ \underline{ \boxed{ \sf{ \blue{ \: 12.5 \: per \: annum. }}}}} \: \bigstar$

Therefore, at 12.5% rate of interest sum will be doubled in 8 years!!

⠀⠀━━━━━━━━━━━━

$\boxed{\begin{minipage}{7 cm}\boxed{\underline{\underline{\bigstar\:\bf\:Extra\:Brainly\:knowlegde\:\bigstar}}}\\\\1) Profit = SP - CP\\\\2) Loss = CP - SP\\\\3) Profit\% = (Profit in Rs.)*100/CP\\\\4) Loss\% = (Loss in Rs.)*100/CP\\\\5) SP = CP*(100+P\%)/100\\\\6) SP = CP*(100-L\%)/100\\\\7) CP = SP*100/(100+P\%)\\\\8) CP = SP*100/(100-L\%)\\\\9) Discount =MP - SP\\\\10) Discount\%=(Discount in Rs.)*100/MP\\\\11) SP = MP*(100-D\%)/100\\\\12) MP = SP*100/(100-D\%)\\\\\end{minipage}}$

Answer 2

$\sf{\underline{\boxed{\large{\blue{\mathsf{Correct\: Question}}}}}}$

• At what rate of interest a certain sum will be doubled in 8 years?

_______________________

$\sf{\underline{\boxed{\large{\blue{\mathsf{Solution}}}}}}$

$\sf{\bold{\green{\underline{\underline{Given}}}}}$

• principle = p
• amount = 2p
• interest = 2p - p = p
• time = 8yrs

_______________________

$\sf{\bold{\green{\underline{\underline{To\:Find}}}}}$

• rate = ?????

______________________

$\sf{\bold{\green{\underline{\underline{Solution}}}}}$

$\sf{\red{\boxed{\bold{Interest =\dfrac{p\times r\times t}{100}}}}}$

$\sf\longrightarrow p = \dfrac{ p \times rate \times 8}{100}$

$\sf\longrightarrow r = \dfrac{ p \times 100}{p\times 8}$

$\sf\longrightarrow r = \dfrac{ 100 }{8}$

$\sf\longrightarrow r = \dfrac{ 50}{4}$

$\sf\longrightarrow r = \dfrac{25}{2}$

$\sf\implies r = 12.5$

_____________________

$\sf{\bold{\green{\underline{\underline{Answer}}}}}$

• principle will be doubled in 8years when the rate is 12.5%