Question

Klaus was replacing the roof on his house. he used 420 nails to attach all the pieces. each pieces of wood needed 7 nails to hold it he used 40 pieces of wood. how many pieces were left?

Answer 1

20 pieces of wood left because....

if you need 7 nails for each piece of wood you have to determine how much wood you have by dividing the total amount of nails by 7 which would get you 60
420/7=60

if you already used 40 pieces then you have 20 left because..
60-40=20