以下の6つの計算問題を解きます。 (19) $\frac{2}{5} + \frac{7}{5} + \frac{1}{7}$ (20) $\frac{17}{11} \times \frac{11}{7} - 2$ (21) $\frac{17}{5} \times \frac{1}{2} - 1$ (23) $3 \div (\frac{1}{4} + 2)$ (24) $\frac{7}{10} \div (4 - \frac{9}{4})$ (25) $5 \div (\frac{12}{7} - 1)$ (26) $1.3 + 1.6 \div 0.5$

1. 問題の内容

以下の6つの計算問題を解きます。

(19) $\frac{2}{5} + \frac{7}{5} + \frac{1}{7}$

(20) $\frac{17}{11} \times \frac{11}{7} - 2$

(21) $\frac{17}{5} \times \frac{1}{2} - 1$

(23) $3 \div (\frac{1}{4} + 2)$

(24) $\frac{7}{10} \div (4 - \frac{9}{4})$

(25) $5 \div (\frac{12}{7} - 1)$

(26) $1.3 + 1.6 \div 0.5$

2. 解き方の手順

(19)

$\frac{2}{5} + \frac{7}{5} + \frac{1}{7} = \frac{9}{5} + \frac{1}{7} = \frac{9 \times 7}{5 \times 7} + \frac{1 \times 5}{7 \times 5} = \frac{63}{35} + \frac{5}{35} = \frac{68}{35}$

(20)

$\frac{17}{11} \times \frac{11}{7} - 2 = \frac{17 \times 11}{11 \times 7} - 2 = \frac{17}{7} - 2 = \frac{17}{7} - \frac{2 \times 7}{7} = \frac{17}{7} - \frac{14}{7} = \frac{3}{7}$

(21)

$\frac{17}{5} \times \frac{1}{2} - 1 = \frac{17 \times 1}{5 \times 2} - 1 = \frac{17}{10} - 1 = \frac{17}{10} - \frac{10}{10} = \frac{7}{10}$

(23)

$3 \div (\frac{1}{4} + 2) = 3 \div (\frac{1}{4} + \frac{8}{4}) = 3 \div \frac{9}{4} = 3 \times \frac{4}{9} = \frac{3 \times 4}{9} = \frac{12}{9} = \frac{4}{3}$

(24)

$\frac{7}{10} \div (4 - \frac{9}{4}) = \frac{7}{10} \div (\frac{16}{4} - \frac{9}{4}) = \frac{7}{10} \div \frac{7}{4} = \frac{7}{10} \times \frac{4}{7} = \frac{7 \times 4}{10 \times 7} = \frac{4}{10} = \frac{2}{5}$

(25)

$5 \div (\frac{12}{7} - 1) = 5 \div (\frac{12}{7} - \frac{7}{7}) = 5 \div \frac{5}{7} = 5 \times \frac{7}{5} = \frac{5 \times 7}{5} = 7$

(26)

$1.3 + 1.6 \div 0.5 = 1.3 + \frac{1.6}{0.5} = 1.3 + 3.2 = 4.5$

3. 最終的な答え

(19) $\frac{68}{35}$

(20) $\frac{3}{7}$

(21) $\frac{7}{10}$

(23) $\frac{4}{3}$

(24) $\frac{2}{5}$

(25) $7$

(26) $4.5$