Answer: [tex]T>2.185[/tex] year
Step-by-step explanation:
[tex]A=P\left ( 1+R/100\right )^{T}[/tex]
[tex]A=Amount ,P=Principle , R=Rate , T=Time[/tex]
CI=compound interest
[tex]CI=A-P[/tex]
[tex]P=400\$[/tex] for each a and b
account earn each year by a=[tex]45\$[/tex]
account b earns [tex]5%[/tex]%
find the time the value of b is more
[tex]45<400\left ( 1+5/100 \right )^{T}-400[/tex]
[tex]445<\left 400\left ( 1+5/100 \right )^{T}[/tex]
[tex]445/400<\left ( 21/20 \right )^{T}[/tex]
[tex]\ln \left ( 445/400 \right )<T\ln \left ( 21/20 \right )[/tex]
[tex].106609735<.0487901642\times T[/tex]
[tex]=2.1850<T[/tex]
[tex]T>2.185[/tex] year