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。