Final answer:
Grayson left an 18% tip on his lunch bill, which is calculated using the formula (tip / total bill) × 100.
Step-by-step explanation:
The question asks to calculate the percentage of the tip left on a lunch bill. To find the percentage tip Grayson left, we need to use the formula for percentage: percent tip = (tip amount / total bill amount) × 100. First, we convert the tip amount of $2.43 and the total bill amount of $13.50 into numbers that can be used in the calculation. Thus, percent tip = ($2.43 / $13.50) × 100.
Next, we divide $2.43 by $13.50, which equals approximately 0.18. Finally, we multiply 0.18 by 100 to get the percentage. Therefore, 0.18 × 100 = 18%. Grayson left an 18% tip for his lunch.