Paddy and Anna each invest $2000 for 5 years.

Paddy earns simple interest at a rate of 1.25% per year.

Anna earns compound interest at a rate of r% per year.

At the end of 5 years, Paddy's investment is worth the same as Anna's investment.

Calculate the value of r.

Respuesta :

Answer: r= 1.22

Step-by-step explanation:

Formula for amount with simple interest = [tex]P(1+rt)[/tex]

, where

P= principal value , r= rate of interest , t = time.

Given: P=  $2000, t= 5 years, r= 1.25% = 0.0125

[tex]A=2000(1+0.0125\times5)\\\\=2000(1.0625)=2125[/tex]

Formula to compute compound amount : [tex]P(1+r)^t[/tex]

[tex]=2000(1+r)^5[/tex]

When both have same worth then

[tex]2000(1+r)^5=2125\\\\\\ (1+r)^5=\dfrac{2125}{2000}\\\\\\ (1+r)^5=1.0625[/tex]

taking log on both sides , we get

[tex]5\ln (1+r)=\ln 1.0625\\\\\\ 5\ln (1+r)=0.0606246\\\\\\ \ln (1+r)=0.012125\\\\\\ 1+r=e^{0.005266}\\\\\\ 1+r=1.0122\\\\ r=0.0122\\\\ \\ r=1.22\%[/tex]

Hence, Value of r= 1.22