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a, \(\dfrac{5\times11\times15\times18}{6\times15\times22\times10}\)
= \(\dfrac{5\times11\times15\times6\times3}{6\times15\times11\times2\times2\times5}\)
= \(\dfrac{5\times11\times15\times6}{5\times11\times15\times6}\) \(\times\) \(\dfrac{3}{2\times2}\)
= 1 \(\times\) \(\dfrac{3}{4}\)
= \(\dfrac{3}{4}\)
b, \(\dfrac{7}{12}\) \(\times\) \(\dfrac{3}{5}\) + \(\dfrac{3}{5}\) \(\times\) \(\dfrac{5}{12}\)
= \(\dfrac{3}{5}\) \(\times\) ( \(\dfrac{7}{12}+\dfrac{5}{12}\))
= \(\dfrac{3}{5}\) \(\times\) \(\dfrac{12}{12}\)
= \(\dfrac{3}{5}\) \(\times\) 1
= \(\dfrac{3}{5}\)
a: \(\dfrac{5}{3}\cdot\dfrac{7}{10}=\dfrac{5}{10}\cdot\dfrac{7}{3}=\dfrac{14}{3}>2\)
\(\dfrac{5}{7}:\dfrac{7}{10}=\dfrac{5}{7}\cdot\dfrac{10}{7}=\dfrac{50}{49}< 2\)
=>\(\dfrac{5}{3}\cdot\dfrac{7}{10}>\dfrac{5}{7}:\dfrac{7}{10}\)
b: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{4}{6}=\dfrac{2}{3}\)
\(\dfrac{8}{9}:\dfrac{4}{3}=\dfrac{8}{9}\cdot\dfrac{3}{4}=\dfrac{8}{4}\cdot\dfrac{3}{9}=\dfrac{2}{3}\)
Do đó: \(\dfrac{4}{5}\cdot\dfrac{5}{6}=\dfrac{8}{9}:\dfrac{4}{3}\)
c: \(\dfrac{5}{11}\cdot\dfrac{33}{15}=\dfrac{5}{15}\cdot\dfrac{33}{11}=\dfrac{3}{3}=1\)
\(\dfrac{6}{17}\cdot\dfrac{34}{25}=\dfrac{34}{17}\cdot\dfrac{6}{25}=2\cdot\dfrac{6}{25}=\dfrac{12}{25}< 1\)
=>\(\dfrac{5}{11}\cdot\dfrac{33}{15}>\dfrac{6}{17}\cdot\dfrac{34}{25}\)
d: \(\dfrac{15}{19}\cdot\dfrac{38}{5}=\dfrac{15}{5}\cdot\dfrac{38}{19}=3\cdot2=6\)
\(\dfrac{15}{16}:\dfrac{3}{8}=\dfrac{15}{16}\cdot\dfrac{8}{3}=\dfrac{15}{3}\cdot\dfrac{8}{16}=\dfrac{5}{2}\)<6
=>\(\dfrac{15}{19}\cdot\dfrac{38}{5}>\dfrac{15}{16}:\dfrac{3}{8}\)
Hướng dẫn giải:
a) 5 x (10 + 9)
Cách 1:
5 x (10 + 9) = 5 x 19 = 95
Cách 2:
5 x (10 + 9) = 5 x 10 + 5 x 9 = 50 + 45 = 95
b) 10 x (30 + 5)
Cách 1:
10 x (30 + 5) = 10 x 35 = 350
Cách 2:
10 x (30 + 5) = 10 x 30 + 10 x 5 = 300 + 50 = 350
Hướng dẫn giải nè :
a) 5 x (10 + 9)
Cách 1:
5 x (10 + 9) = 5 x 19 = 95
Cách 2:
5 x (10 + 9) = 5 x 10 + 5 x 9 = 50 + 45 = 95
b) 10 x (30 + 5)
Cách 1:
10 x (30 + 5) = 10 x 35 = 350
Cách 2:
10 x (30 + 5) = 10 x 30 + 10 x 5 = 300 + 50 = 350
a)x-3/4=5/12 : 10/3
x-3/4= 1/8
x = 1/8 + 3/4
x = 7/8
b)7/6 - x=3/5 x 15/18
7/6 - x = 1/2
x = 7/6 - 1/2
x = 2/3
a)x-3/4=5/12 : 10/3
x-3/4= 1/8
x = 1/8 + 3/4
x = 7/8
b)7/6 - x=3/5 x 15/18
7/6 - x = 1/2
x = 7/6 - 1/2
x = 2/3
x+1+2+3+....+100 = 250000
x + 5050 = 250000
x = 250000 - 5050
x = 2244950
a, \(\frac{2}{3}:\frac{5}{7}:\frac{x}{9}=\frac{2}{7}:\frac{3}{5}:\frac{10}{9}\Leftrightarrow\frac{2\times7\times9}{3\times5\times x}=\frac{2\times5\times9}{7\times3\times10}\Leftrightarrow\frac{42}{5\times x}=\frac{3}{7}\Leftrightarrow294=15\times x\Leftrightarrow x=19,6\)
Các phần sau tương tự.
Dùng phương pháp nhân chéo và kiểm tra trình độ tính toán, khả năng rút gọn.
Thay kết quả vào x để kiểm tra lại bài.
Bài 1:
a) \(x.\dfrac{3}{4}=\dfrac{9}{14}\)
\(\Rightarrow x=\dfrac{9}{14}:\dfrac{3}{4}\)
\(\Rightarrow x=\dfrac{6}{7}\)
b) \(x:\dfrac{5}{9}=\dfrac{3}{10}\)
\(\Rightarrow x=\dfrac{3}{10}.\dfrac{5}{9}\)
\(\Rightarrow x=\dfrac{1}{6}\)
\(\frac{3}{5}+\frac{x}{35}=\frac{5}{7}\)
\(\frac{5}{7}-\frac{3}{5}=\frac{4}{35}\)
Vậy x= 4
Chúc bạn may mắn!
= 75 + 15 - 250
= 90 - 250 = - 160
xin tiick
câu trả lời cho bạn là 65 nhé bạn