小5算数 分数のたし算ひき算８
小数と分数にチャレンジ！
帯分数に通分，今回は小数も混ざった問題が出てきます。
めざせ！分数マスター！
＜問題＞
次の①～④の計算をしよう！
① \(\displaystyle 1\frac{1}{3}+\frac{3}{4}=\)
② \(\displaystyle \frac{8}{15}-\frac{1}{3}=\)
③ \(\displaystyle 2\frac{1}{3}-\frac{9}{4}=\)
④ \(\displaystyle \frac{3}{5}+0.3=\)
正解はこちら！
① \(\displaystyle 1\frac{1}{3}+\frac{3}{4}\)
\(\displaystyle =1\frac{1×4}{3×4}+\frac{3×3}{4×3}\)
\(\displaystyle =1\frac{4}{12}+\frac{9}{12}\)
\(\displaystyle =1\frac{13}{12}\)
\(\displaystyle =2\frac{1}{12}\)
② \(\displaystyle \frac{8}{15}-\frac{1}{3}\)
\(\displaystyle =\frac{8}{15}-\frac{1×5}{3×5}\)
\(\displaystyle =\frac{8}{15}-\frac{5}{15}\)
\(\displaystyle =\frac{3}{15}\)
\(\displaystyle =\frac{1}{5}\)
③ \(\displaystyle 2\frac{1}{3}-\frac{9}{4}\)
この問題，ひき算でのくり下げがたいへん！
\(\displaystyle =2\frac{1×4}{3×4}-\frac{9×3}{4×3}\)
\(\displaystyle =2\frac{4}{12}-\frac{27}{12}\)
\(\displaystyle =1\frac{4+12}{12}-\frac{27}{12}\)
\(\displaystyle =\frac{4+12+12}{12}-\frac{27}{12}\)
\(\displaystyle =\frac{28}{12}-\frac{27}{12}\)
\(\displaystyle =\frac{1}{12}\)
④ \(\displaystyle \frac{3}{5}+0.3\)
0.1は\(\displaystyle \frac{1}{10}\)だから，0.3は\(\displaystyle \frac{3}{10}\)だね！
\(\displaystyle =\frac{3}{5}+\frac{3}{10}\)
\(\displaystyle =\frac{3×2}{5×2}+\frac{3}{10}\)
\(\displaystyle =\frac{6}{10}+\frac{3}{10}\)
\(\displaystyle =\frac{9}{10}\)
全問正解できたかな？
③と④は難しめですが，ぜひチャレンジしてみてくださいね。