Maths Olympiad Prep

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Problem 314

Geometry Difficulty 2.3 Find the answer CEMC Cayley

A solid rectangular prism has dimensions 4 by 2 by 2. A 1 by 1 by 1 cube is cut out of the corner creating the new solid shown. What is the surface area of the new solid?

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

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Official solution

The original prism has four faces that are 4 by 2 rectangles, and two faces that are 2 by 2 rectangles. Thus, the surface area of the original prism is 4(42)+2(22)=32+8=40 4(4 \cdot 2)+2(2 \cdot 2)=32+8=40 . When a 1 by 1 by cube is cut out, a 1 by 1 square is removed from each of three faces of the prism, but three new 1 by 1 squares become part of the surface area. In other words, there is no change to the total surface area. Therefore, the surface area of the new solid is also 40.

Source: Omni-MATH, licensed Apache-2.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.