Read the word problem. Look at the student work and solution. Identify the error and describe it. Solve the problem correctly. Then share a strategy this student could use to prevent the same error in the future.
What is the total cost of a sweatshirt if the regular price is $42 and the sales tax is 5.75%?
Student work:
Regular price of sweatshirt: $42
Sales tax: 5.75%
Solution:
Step 1: Find the amount of sales tax by multiplying the regular price by the sales tax rate.
Sales tax = $42 * 5.75% = $2.41
Step 2: Add the sales tax to the regular price to find the total cost.
Total cost = $42 + $2.41 = $44.41
Error:
The student has made an error in calculating the sales tax. The student mistakenly calculated 5.75% of $42 as $2.41, which is incorrect.
Correct solution:
Step 1: Convert the sales tax rate from a percentage to a decimal by dividing it by 100.
Sales tax rate = 5.75 / 100 = 0.0575
Step 2: Find the amount of sales tax by multiplying the regular price by the sales tax rate.
Sales tax = $42 * 0.0575 = $2.415
Round off to the nearest cent:
Sales tax = $2.42
Step 3: Add the sales tax to the regular price to find the total cost.
Total cost = $42 + $2.42 = $44.42
Strategy to prevent the same error in the future:
The student could double-check their calculations by using a calculator or by using estimation to ensure the answer they get is reasonable. Additionally, it would be helpful for the student to be aware of the proper method of calculating sales tax by converting the percentage to a decimal before multiplying.