Math help please

Question

A state charges an 8.5% sales tax and a 10% excise tax on gasoline. Nandin purchased $25 of gasoline before taxes were added. How should Nandin find the total tax on his purchase?

A Multiply 25 by 0.1, then multiply 25 by 0.085, and then subtract the smaller sum from the larger.

BMultiply 25 by 18.5.

C Multiply 25 by 0.085, then multiply 25 by 0.1, and then add the two sums.

Answer 1

Let's investigate the 3 choices.

The $25 for gasoline alone is fixed in all cases as are the 10% excise tax and 8.5% sales tax.

a.) This option says multiply $25 by 0.1 and again multiply $25 by 0.085 and subtract the smaller product from the larger. $25 x 0.1 = $2.50 and $25 x 0.085 = $2.125~ $2.13. The difference is $0.37. However the problem states that both sales AND excise taxes are collected, not the difference, so this is clearly NOT the answer.

b.) Multiply $25 by 18.5, which is $462.5. This is NOT the solution, because 18.5 is not presented as a percentage or a proportion.

c.) Multiply $25 by 0.085 and again multiply $25 by 0.1 and add the amounts. The products were found in part a) as $2.125 and $2.50. Add them together to get $4.625 ~ $4.63. This IS the solution. Notice this is equivalent to multiplying $25 by 0.10+0.085 = $25*0.185, which is the multiplier in b.)/100.