Question

Lucas orders some tennis balls from online shopping. Each tennis ball costs $\$20$ and the shipping fee is $\$5$ regardless of the number of tennis balls. If Lucas spent a total of $\$105,$ how many tennis balls did he order?

• A. $5$
• B. $4$
• C. $10$
• D. $15$

Answer 1

The correct option is A $5$

Cost of each tennis ball $=\$20$
Let the number of tennis ball be $\$x$.
Total cost of $x$ tennis balls $=\$x\times 20=\$20x$
Total money spent by Lucas $=\$105$

$\text{Total cost of}x\text{tennis balls + Shipping fee = Total money spent}$
$\Rightarrow 20x+5=105$

Step 1: Subtract 5 from both sides of the equation to eliminate the constant on the left side of the equation.
$20x+5-5=105-520x=100$

Step 2: Now, divide both sides by 20 to eliminate 20 on the left side of the equation.
$\frac{20x}{20}=\frac{100}{20}x=5$

Hence, Lucas ordered 5 tennis balls.