Peter is at a lumber yard. He gets 2 free boxes of nails for every 10 boards he buys. Write an expression for the number of boxes of nails Peter will get if he buys n boards. If each box has 100 nails, explain how to write an expression to find how many nails Peter will have if he purchases 90 boards.

a. The number of 10-boards Peter bought is equal to n divided by 10. Then, each of the 10-boxes will get two boxes of nails. The number of boxes of nails that Peter will have after buying n boards will be,

    N = (2)(n/10)

Simplifying,

   N = n/5

b. If the number of boards are 90 then,

     N2 = (90/10)(2)(100 nails/box)
     N2 = 1800

Answer: 1800