Question

Every corner of a rectangular prism is cut off by a straight slice through the three edges meeting at that corner, removing a small triangular piece at each of the eight corners. How many edges does the new figure have?

$24$

$30$

$36$

$42$

$48$

Solution:

A rectangular prism starts with $12$ edges, and cutting corners only shortens them without removing any.

Each of the $8$ corner cuts creates a small triangular face with $3$ new edges, adding $8 \cdot 3 = 24$ edges. The total is $12 + 24 = 36$ .

Thus, the correct answer is C .

1990 AMC 8 Problem 18

Solution:

Problem 18 in Other Years