並前往https://zh.khanacademy.org/math/zh-grade-3/xf2f7ddeeb5caa97a:zh-v2-chang-fang-xing-de-zhou-chang-he-mian-ji/xf2f7ddeeb5caa97a:zh-v2-chang-fang-xing-mian-ji/v/rectangle-area-as-product-of-dimensions-same-as-counting-unit-squares