Thread: Find the Cost

A store advertises that during its Labor Day sale $15 will be deducted from every purchase over $100. In addition, after the deduction is taken, the store offers an early-bird discount of 20% to any person who makes a purchase before 10 a.m. If Hakeem makes a purchase of x dollars,
x > 100, at 8 a.m., what, in terms of x, is the cost of Hakeem’s purchase?

(1) 0.20x - 15 (3) 0.85x - 20
(2) 0.20x -3 (4) 0.80x - 12...This is the answer.


MY Work:

I understand the situation in the question. The correct answer is highlighted in red. I selected choice (1) given the fact that Hakeem purchased an item over $100 and that the store offers a discount of $15 and an additional discount of 20%.

It made sense to easily come up with 0.20x - 15. In fact, I also decided to let C = cost and then went on to develop the equation C = 0.20x - 15.

Why is choice (4) correct and my answer incorrect?

Originally Posted by magentarita

A store advertises that during its Labor Day sale $15 will be deducted from every purchase over $100. In addition, after the deduction is taken, the store offers an early-bird discount of 20% to any person who makes a purchase before 10 a.m. If Hakeem makes a purchase of x dollars,
x > 100, at 8 a.m., what, in terms of x, is the cost of Hakeem’s purchase?

(1) 0.20x - 15 (3) 0.85x - 20
(2) 0.20x -3 (4) 0.80x - 12...This is the answer.


MY Work:

I understand the situation in the question. The correct answer is highlighted in red. I selected choice (1) given the fact that Hakeem purchased an item over $100 and that the store offers a discount of $15 and an additional discount of 20%.

It made sense to easily come up with 0.20x - 15. In fact, I also decided to let C = cost and then went on to develop the equation C = 0.20x - 15.

Why is choice (4) correct and my answer incorrect?

You've subtracted the 20% discount before the $15 deduction. The 20% discounted is subtracted after the $15 deduction.

(x - 15) - 20% of (x - 15) = .

Originally Posted by mr fantastic

You've subtracted the 20% discount before the $15 deduction. The 20% discounted is subtracted after the $15 deduction.

(x - 15) - 20% of (x - 15) = .

I did not keep the order.

Got it.