Track / Stage 4 / 27 of 340 #287 of 1964

Problem 287

AMC 12 late, AIME early

Combinatorics Difficulty 4.5 Multiple choice

As shown in Figure 7, the shaded part is composed of three small squares on the grid paper, and such a pattern is called an "L-shape". Therefore, on a grid paper composed of $4 \times 5$ small squares, the number of different L-shape patterns that can be drawn is:

Pick one

Official solution

(提示: each $2 \times 2$ small square L-shaped pattern has four different ways to be drawn, and there are 12 different positions for the $2 \times 2$ small square patterns, so the number of L-shaped patterns in different positions is $12 \times 4=48$ .)

Source: NuminaMath-1.5, licensed Apache-2.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.