Question 283082
we have 4*1/4 =1 penny 
area of a penny  pi*(d/2)^2=3.14*d^2/4=3.14/4*d^2

area of the square is d^2
3.14/4 *100 is the percentage of the square covered by the pennies
3.14/4 *100=78.5
so b) 70-80