Final answer:
To estimate the total cost of the bill including tax and tip, multiply the bill amount by the tip percentage and sales tax rate.
Step-by-step explanation:
To estimate the approximate total cost of the bill including tax and tip, you can use mental math. First, find the 15% tip by multiplying the total bill amount ($38.96) by 0.15. This gives you a tip amount of $5.84.
Next, find the sales tax amount by multiplying the total bill amount ($38.96) by the sales tax rate in decimal form (0.0875). This gives you a sales tax amount of $3.41.
Finally, add the total bill amount, tip amount, and sales tax amount together to get the approximate total cost of the bill including tax and tip. Rounding to the nearest dollar, the total cost would be approximately $48.