Presentation on theme: "By: Ashley, Kelsey, Devin, Jarred, Shaq. Surface area formula SA=4πr^2 Finding a radius EX. SA=30in plug it back into formula SA=4πr^2 30in=4πr^2."— Presentation transcript:
Surface area formula SA=4πr^2 Finding a radius EX. SA=30in plug it back into formula SA=4πr^2 30in=4πr^2 divide by 4π to both sides 2.38in=r^2 then your Square root 2.38in=√r^2 R=1.55in Now plugging it back into the formula to find SA SA=4πr^2 SA=4π(1.55in)^2 SA=30in^2 Remember to square your units cause its SA
Volume Formula V=4/3πr^3 Finding the radius EX. V=60cm V=4/3πr^3 Plug in 60 for V 60cm=4/3πr^3 Divide by 4/3π to both sides 14.3239cm=r^3 Then you Cube root 2.42cm=r Plugging It back in. V=4/3πr^3 V=4/3π(2.42)^3 V=60 And remember if you have a diameter of 16 or any number to find radius just divide by 2
MM2G4B Determining the effect on surface area and volume of changing the radius of a sphere.
Surface area When you double the radius the surface area changes by a multiple of 4 So, when you triple the radius the surface area changes by a multiple of 9 Double (2) radius X4 Triple (3) radius X9
Volume If you double the radius the volume changes to a multiple of 8 So, if you triple the radius the volume changes to a multiple of 27 Double (2) radius X8 Triple (3) radius X27
Examples of surface area SA=4πr² R=1 SA=4π(1)² SA=4π1 SA=4π SA=12.6 Double it R=2 SA=4π(2)² SA=4π4 SA=16π SA=50.3 12.6 x 4 SA=50.4
Examples of Volume V=4πr³/3 R=4 V=4π(4)³/3 V=85.3 Double it r=8 V=4π(8)³/3 V=682.7 V=85.3 x 8=682.4
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