10% of 640 is 64. So 640-64= 576 fans. Then after the five touchdowns 26% of 576 is 144 . So 576-144= 432 fans left
So...the diameter is increasing at a rate if 2cm/minute, therefore the radius (1/2 the diameter) is increasing at half the rate. You will learn how to calculate the rate of change at a specific point in time in calculus.
Just count the number of squares:
(9+5)*2=14*2=28
