Question

Barbara buys a box of pens for $4. For every additional box she buys, she gets a $1 discount. Which expression represents the total cost of the pens, c, as a function of the number of boxes, b?

Answer 1

Answer:

The cost of the first box is fixed at $4. The total number of boxes is b. If we remove the first box bought, we are left with b-1 boxes. The cost per box of these b-1 boxes will be found after the discount of $1 per box. So, the cost of each of the b-1 boxes is $3.

If we combine the cost of the first box and the total cost of the other boxes, the total cost function becomes:

c=4+3(b−1)