Tính bằng cách thuận tiện. A 5/9 x 8/17 + 4/9 x 8/17 b 7/9 — Không quảng cáo

Tính bằng cách thuận tiện a) \(\frac{5}{9} \times \frac{8}{{17}} + \frac{4}{9} \times \frac{8}{{17}}\) b) \(\frac{7}{9} \times \frac{{11}}{{13}} \times \frac{{27}}{7} \times \frac{{26}}{{11}}\)

Đề bài

Tính bằng cách thuận tiện.

a) \(\frac{5}{9} \times \frac{8}{{17}} + \frac{4}{9} \times \frac{8}{{17}}\)

b) \(\frac{7}{9} \times \frac{{11}}{{13}} \times \frac{{27}}{7} \times \frac{{26}}{{11}}\)

Phương pháp giải

a)

\(\begin{array}{l}\frac{5}{9} \times \frac{8}{{17}} + \frac{4}{9} \times \frac{8}{{17}}\\ = \frac{8}{{17}} \times (\frac{5}{9} + \frac{4}{9})\\ = \frac{8}{{17}} \times \frac{9}{9}\\ = \frac{8}{{17}} \times 1 = \frac{8}{{17}}\end{array}\)

b)

\(\begin{array}{l}\frac{7}{9} \times \frac{{11}}{{13}} \times \frac{{27}}{7} \times \frac{{26}}{{11}}\\ = \frac{{7 \times 11 \times 9 \times 3 \times 13 \times 2}}{{9 \times 13 \times 7 \times 11}}\\ = 6\end{array}\)

a)

\(\begin{array}{l}\frac{5}{9} \times \frac{8}{{17}} + \frac{4}{9} \times \frac{8}{{17}}\\ = \frac{8}{{17}} \times (\frac{5}{9} + \frac{4}{9})\\ = \frac{8}{{17}} \times \frac{9}{9}\\ = \frac{8}{{17}} \times 1 = \frac{8}{{17}}\end{array}\)

b)

\(\begin{array}{l}\frac{7}{9} \times \frac{{11}}{{13}} \times \frac{{27}}{7} \times \frac{{26}}{{11}}\\ = \frac{{7 \times 11 \times 9 \times 3 \times 13 \times 2}}{{9 \times 13 \times 7 \times 11}}\\ = 6\end{array}\)