Sound, earthquakes, the brightness of stars, and chemistry, such as pH balance, a measure of acidity and alkalinity, are all instances of this.
I think that 3 rolls is wrong and that 6 rolls is right. If you create a 15 by 15 square and draw two lines through the center that connect to the opposite corner, you'll be able to use the Pythagorean Theorem.
Perimeter: 15+15+15+15=60ft.
Length of Line from Corner to Corner:
(15)(15)+(15)(15)=C^2
225+225=C^2
450=C^2
21.2=C
21.2(2)= 42.4ft.
42.4ft.+60ft.= 102.4ft.
102.4ft. divided by 20ft. = 5.12 = <u>6 rolls</u>
You could do :
Johnny was financing a limited editions Xbox One S. The price was $420 and he put down 40%. How much is left to be financed?
dp=420(40/100)=16800/100=168
then you would subtract 420-168 which would give you 252
;) good luck !!