what is the total cost of these paper clips

Question

each paper clip is 7/8 of an inch long and cost 0.03. exactly enough paper clips are laid end to end to have a total length of 56 inches. what is the total cost of these paper clips

Answer 1

This problem can be solved using the Multiplicative Identity (that is, 1) because we want to change the units (for 56 inches of wire) without changing the value.

 

We need the following information:

    7/8 inch    costs   $0.03       [so, (7/8 inches)/($0.03) = 1]   also  [ ($0.03)/(7/8 inches) = 1]

 

O.K.,

          56 inches

          (56 inches)*1

          (56 inches)*( ($0.03)/(7/8 inches) )         [note: inches cancel, leaving only $]

          (56)*($0.03)/(7/8)

          (56)*($0.03)*(8/7)                [to divide by fraction, invert and multiply]

           $1.92