Since the first amount given is $15, we can begin by calculating 15 % of 15. To do this, we can use the percent proportion.
a/b=p/100
In the above formula, a is the part, b the base, and p the percent. By substituting the price of the meal for b, and 15 for p, we can find the part a that constitutes 15 % of the meal.
Therefore, the tip we would pay on a $15 bill is $2.25. When we entered the restaurant we had $55. To determine the amount we have left after paying the bill and adding a 15 % tip, we add the cost of the tip to the bill, and subtract the sum from 55.
55 - (15 + 2.25) = $37.75
The following table shows the corresponding tip amounts for the given amounts and how much money we have left after paying.
Cost of Meal, c
Cost + Tip
Total Cost
$55 - Total cost
$15
15+0.15 * 15
17.25
$37.75
$21
21+0.15 * 21
24.15
$30.85
$24
24+0.15 * 24
27.60
$27.40
$30
30+0.15 * 30
34.50
$20.50
b
To determine the amount of money we have left after paying the bill and a 15 % tip, we will follow three steps.
Determine the amount of the tip, 0.15c.
Add the tip to the cost of the bill, c+0.15c.
Subtract the total cost from $55.
This work is shown in Part A. We can write an equation for this. Let m be the amount of money we have left after paying the cost of the meal c and a tip of 15 %.
m = 55 - (c +0.15c)
⇕
m=55-1.15c
