Chapter 7.5, Problem 37STP

To determine

To calculate: The cost of dinner without tip.

Answer to Problem 37STP

The cost of dinner alone without the tip is $38.

Explanation of Solution

Given information:The total cost of dinner including 15% tip was $43.70.

Calculation:

Let the cost of dinner alone without the tip be $ x .

The tip is 15% of the cost of dinner.

15% of x is

  $x\times \frac{15}{100}=\frac{15x}{100}$

Total cost of dinner including tip

  $\begin{array}{l}(x+\frac{15x}{100})\\ =\frac{100x}{100}+\frac{15x}{100}\\ =\frac{100x+15x}{100}\\ =\frac{115x}{100}\end{array}$

Total cost of dinner including tip given $43.70.

We can write,

  $\begin{array}{l}\frac{115x}{100}=43.70\\ \Rightarrow 115x=43.70\times 100\\ \Rightarrow 115x=4370\\ \Rightarrow x=\frac{4370}{115}\\ \Rightarrow x=38\end{array}$

  $\therefore$ The cost of dinner alone without the tip is $38.

Option A is correct.