9. the owner of a bookstore buys used books from customers for $1.50 each. the owner then resells the books…

9. the owner of a bookstore buys used books from customers for $1.50 each. the owner then resells the books for 400% of the amount he paid for them. what is the price of a used book in his bookstore? a. $4.00 b. $4.50 c. $6.00 d. $7.50

9. the owner of a bookstore buys used books from customers for $1.50 each. the owner then resells the books for 400% of the amount he paid for them. what is the price of a used book in his bookstore? a. $4.00 b. $4.50 c. $6.00 d. $7.50

Answer

Explanation:

Step1: Set up the percentage - increase formula

Let the cost price (the amount the owner paid) be $C = 1.50$ dollars and the selling price be $S$. The percentage increase is 400%. The formula for percentage increase is $\text{Percentage Increase}=\frac{S - C}{C}\times100%$.

Step2: Substitute the values into the formula

We know that 400%=$\frac{S - 1.50}{1.50}\times100%$. First, divide both sides of the equation by 100% to get 4=$\frac{S - 1.50}{1.50}$.

Step3: Solve for $S$

Multiply both sides of the equation 4=$\frac{S - 1.50}{1.50}$ by 1.50: $4\times1.50=S - 1.50$. Then $6 = S- 1.50$. Add 1.50 to both sides of the equation: $S=6 + 1.50=7.50$.

Answer:

D. $7.50$