\(\dfrac{5}{6}\times\) \(\dfrac{1}{5}\) x \(\dfrac{6}{5}\) = \(\dfrac{1}{5}\)

\(\dfrac{8}{7}\) x \(\dfrac{4}{9}\) x \(\dfrac{9}{32}\) = \(\dfrac{1}{7}\)

\(\dfrac{5}{6}-\dfrac{1}{5}\) x \(\dfrac{6}{5}=\dfrac{1}{5}\)

\(\dfrac{8}{7}-\dfrac{4}{9}\) x \(\dfrac{9}{32}=\dfrac{1}{7}\)

a; \(\dfrac{1}{6}\) + \(\dfrac{2}{3}\)

= \(\dfrac{1}{6}\) + \(\dfrac{4}{6}\)

= \(\dfrac{5}{6}\)

b; \(\dfrac{3}{7}\) + \(\dfrac{4}{21}\)

= \(\dfrac{9}{21}+\dfrac{4}{21}\)
= \(\dfrac{13}{21}\)

c; \(\dfrac{5}{4}\) + \(\dfrac{3}{32}\)

= \(\dfrac{40}{32}\) + \(\dfrac{3}{32}\)

= \(\dfrac{43}{32}\)

d; \(\dfrac{5}{12}\) + \(\dfrac{1}{4}\)

= \(\dfrac{5}{12}+\dfrac{3}{12}\)

= \(\dfrac{8}{12}\)

= \(\dfrac{2}{3}\)

a: \(\dfrac{1}{6}+\dfrac{2}{3}=\dfrac{1}{6}+\dfrac{4}{6}=\dfrac{5}{6}\)

b: \(\dfrac{3}{7}+\dfrac{4}{21}=\dfrac{9}{21}+\dfrac{4}{21}=\dfrac{13}{21}\)

c: \(\dfrac{5}{4}+\dfrac{3}{32}=\dfrac{40}{32}+\dfrac{3}{32}=\dfrac{43}{32}\)

d: \(\dfrac{5}{12}+\dfrac{1}{4}=\dfrac{5}{12}+\dfrac{3}{12}=\dfrac{8}{12}=\dfrac{2}{3}\)

Bài 3: 

a; \(\dfrac{1}{6}\) + \(\dfrac{3}{2}\) + \(\dfrac{1}{2}\)

= \(\dfrac{1}{6}\) + \(\dfrac{9}{6}\) + \(\dfrac{3}{6}\)

= \(\dfrac{13}{6}\) 

b; \(\dfrac{3}{8}+\dfrac{1}{2}+\dfrac{1}{8}\)

= (\(\dfrac{3}{8}+\dfrac{1}{8}\)) + \(\dfrac{1}{2}\)

= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\)

 = 1

Bài 4:

 a; \(\dfrac{2}{5}+\dfrac{6}{10}+\dfrac{3}{5}\)

= \(\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{3}{5}\)

= \(\dfrac{8}{5}\)

b; \(\dfrac{1}{7}+\dfrac{4}{14}+\) \(\dfrac{3}{7}\)

= \(\dfrac{1}{7}+\dfrac{2}{7}+\dfrac{3}{7}\)

= \(\dfrac{6}{7}\)

\(A=\left(1-\dfrac{1}{2}\right)\times\left(1-\dfrac{1}{3}\right)\times...\times\left(1-\dfrac{1}{2018}\right)\)

\(=\dfrac{1}{2}\times\dfrac{2}{3}\times...\times\dfrac{2017}{2018}\)

\(=\dfrac{1}{2018}\)

Chiều dài hơn 1/34 cạnh hình vuông bao nhiêu cm thế em?

Độ dài cạnh hình vuông:

48 : 4 = 12 (cm)

Chu vi hình chữ nhật:

12 × 2 × 2 = 48 (cm)

Diện tích hình vuông:

12 × 12 = 144 (cm²)

Cạnh hình vuông là: 48 : 4 = 12 (cm)

Chu vi của hình chữ nhật là: 12 x 2 x 2  = 48 (cm)

Diện tích hình vuông là: 12 x 12 = 144 (cm²)

Đáp số: ... 

Câu 2

Số vòng chú Sơn có thể quấn:

125/2 : 5/6 = 75 (vòng)

\(\dfrac{2}{3}\) x \(\dfrac{5}{4}\) + \(\dfrac{2}{3}\) x \(\dfrac{4}{5}\) = \(\dfrac{2}{3}\)  x (\(\dfrac{5}{4}+\dfrac{4}{5}\))

Vậy phân số tối giản cần điền vào chỗ... là \(\dfrac{2}{3}\)