feng invests money in an account paying simple interest. he invests $70 and no money is added or removed…

Explanation:

Step1: Calculate the interest amount

The interest $I$ is the final amount minus the principal. So $I = 70.70 - 70=0.70$.

Step2: Use the simple - interest formula

The simple - interest formula is $I = Prt$, where $P$ is the principal amount, $r$ is the annual interest rate (in decimal form), and $t$ is the time in years. Here, $P = 70$, $t = 1$ year, and $I = 0.70$. Substituting these values into the formula gives $0.70=70\times r\times1$.

Step3: Solve for $r$

To find $r$, we divide both sides of the equation $0.70 = 70r$ by 70. So $r=\frac{0.70}{70}=0.01$.

Step4: Convert $r$ to a percentage

To convert the decimal $r = 0.01$ to a percentage, we multiply by 100. So the percentage interest rate is $0.01\times100 = 1%$.

Answer:

$1%$