Big Ideas Math: Modeling Real Life, Grade 8
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Big Ideas Math: Modeling Real Life, Grade 8 View details
4. Surface Areas and Volumes of Similar Solids
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Exercise 4 Page 447

When two solids are similar, the ratio of their surface areas is equal to the ratio of their corresponding linear measures squared.

171.9 square centimeters

Practice makes perfect

We know the diameter of two similar cylinders but the surface area of just one of them.

prisms
We will use the fact that these cylinders are similar to find the suface area of the bigger cylinder. When two solids are similar, the ratio of their surface areas is equal to the ratio of their corresponding diameters squared. Surface area of the smaller cylinder/Surface area of the bigger cylinder = (Diameter of the smaller cylinder/Diameter of the bigger cylinder)^2 We know that the diameter and the surface area of the smaller cylinder are 4 centimeters and 110 square centimeters, respectively. We also know that the diameter of the bigger cylinder is 5 centimeters. If we let S be the surface area of the bigger cylinder, we can substitute these values into the equation and solve for S.
Surface area of the smaller cylinder/Surface area of the bigger cylinder=(Diameter of the smaller cylinder/Diameter of the bigger cylinder)^2
110/S=(4/5)^2
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Solve for S
110/S=4^2/5^2
110/S=16/25
110=16/25 * S
110=16 * S/25
110 * 25=16 * S
2750=16 S
2750/16=S
171.875=S
S=171.875
S=171.9
The surface area of the bigger cylinder is about 171.9 square centimeters.