分数の割り算

===== 小学 =====
1 ÷ 3 = 1/3
2 ÷ 5 = 2/5

これより
1 ÷ 3 = 1 × 1/3 = 1/3
2 ÷ 5 = 2 × 1/5 = 2/5

ポイントは、逆数して掛け算をすること。
2 ÷ 2/3 = 2 × 3/2 = 3
2/5 ÷ 3/2 = 2/5 × 2/3 = 4/15

＜まとめ＞
a ÷ b = a × 1/b = a/b
a ÷ b/c = a × c/b = ac/b
a/b ÷ c/d = a/b × d/c = ad/bc