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28 + 94 + 6 + 372 = ( 94 + 6 ) + ( 28 + 372 )
= 100 + 400
= 500
7/8 + 5/6 = 41/24
4/8 : 3/5 = 5/6
Bài 1:
\(\dfrac{2}{3}\) + \(\dfrac{3}{4}\) - \(\dfrac{2}{5}\)
=\(\dfrac{40}{60}\) + \(\dfrac{45}{60}\) - \(\dfrac{24}{60}\)
= \(\dfrac{61}{60}\)
b; \(\dfrac{12}{13}\) x \(\dfrac{3}{4}\) - \(\dfrac{7}{13}\)
= \(\dfrac{9}{13}\) - \(\dfrac{7}{13}\)
= \(\dfrac{2}{13}\)
c; \(\dfrac{15}{17}\) : \(\dfrac{19}{34}\) - \(\dfrac{17}{19}\)
= \(\dfrac{15}{17}\) x \(\dfrac{34}{19}\) - \(\dfrac{17}{19}\)
= \(\dfrac{30}{19}\) - \(\dfrac{17}{19}\)
= \(\dfrac{13}{19}\)
Bài 2:
a; \(\dfrac{x}{5}\) x \(\dfrac{3}{7}\) = \(\dfrac{9}{35}\)
\(\dfrac{x}{5}\) = \(\dfrac{9}{35}\) : \(\dfrac{3}{7}\)
\(\dfrac{x}{5}\) = \(\dfrac{3}{5}\)
\(x\) = \(\dfrac{3}{5}\) x 5
\(x\) = 3
a) 13/28 = 7/28 + 4/28 + 2/28 = 1/4 + 1/7 + 1/14
b) 29/45 = 15/45 + 9/45 + 5/45 = 1/3 + 1/5 + 1/9
Hok tốt !
#Minh#
BÀI 1:
a) \(\frac{4}{5}+\frac{3}{8}+\frac{1}{4}\)
\(=\frac{32}{40}+\frac{15}{40}+\frac{10}{40}\)
\(=\frac{32+15+10}{40}\)\(=\frac{57}{40}\)
b) \(\frac{5}{9}+\frac{2}{3}+\frac{1}{2}\)
\(=\frac{10}{18}+\frac{12}{18}+\frac{9}{18}\)
\(=\frac{10+12+9}{18}=\frac{31}{18}\)
\(a,\left(\frac{5}{7}+\frac{9}{7}\right)x\frac{21}{28}\)
\(C1:=\frac{14}{7}x\frac{21}{28}=\frac{3}{2}\)
\(C2:=\frac{5}{7}x\frac{21}{28}+\frac{9}{7}x\frac{21}{28}=\frac{15}{28}+\frac{27}{28}=\frac{3}{2}\)
\(b,\frac{4}{5}x\frac{13}{14}+\frac{13}{14}x\frac{1}{5}\)
\(C1:=\frac{26}{35}+\frac{13}{70}=\frac{13}{14}\)
\(C2:=\frac{13}{14}x\left(\frac{4}{5}+\frac{1}{5}\right)=\frac{13}{14}x1=\frac{13}{14}\)
học tốt ~~~
4/5 * x = 13/28
x = 13/28 : 4/5
x = 13/28 * 5/4
x = 65/112
x=13/35