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a) x : ( 12 x 15 ) = 8/3 x 4 x 15
x : 180 = 160
x = 160 : 180
x = 8/9
Vậy x = 8/9
b) ( 1/2 x 2/3 x 3/4 x 4/5 ) : x = 1 x 2 x 3 x 4/ 5 x 6 x 7 x 8
1/5 : x = 1/70
x = 1/5 : 1/70
x = 14
Vậy x = 14
\(\dfrac{15\times24+12\times15}{30\times18}=\dfrac{15\times\left(24+12\right)}{30\times18}=\dfrac{15\times36}{30\times18}=\dfrac{3\times5\times6\times6}{6\times5\times3\times6}=1\)
=\(\dfrac{15\times\left(24+12\right)}{30\times18}\)= \(\dfrac{15\times36}{540}\)=\(\dfrac{540}{540}\)=1
3/3x6 + 3/6x9 + 3/9x12 + 3/12x15 + 3/15x18
= 1/3 - 1/6 + 1/6 - 1/9 + ... + 1/15 - 1/18
= 1/3 - 1/18
= 5/18
\(\frac{3}{3\times6}+\frac{3}{6\times9}+\frac{3}{9\times12}+\frac{3}{12\times15}+\frac{3}{15\times18}\)
=\(3\times\left(\frac{1}{3\times6}+\frac{1}{6\times9}+\frac{1}{9\times12}+\frac{1}{12\times15}+\frac{1}{15\times18}\right)\)
=\(3\times\left(\frac{1}{3}\times\frac{1}{6}+\frac{1}{6}\times\frac{1}{9}+\frac{1}{9}\times\frac{1}{12}+\frac{1}{12}\times\frac{1}{15}+\frac{1}{15}\times\frac{1}{18}\right)\)
=\(3\times\left(\frac{1}{3}\times\frac{1}{18}\right)\)
=\(3\times\frac{1}{54}=\frac{3}{54}=\frac{1}{18}\)
4 x 18 x 25 + (142 x 12 + 142 x 18)
= (4 x 25) x 18 + (142 x (12 + 18))
= 100 x 18 + (142 x 30)
= 1800 + 4260
= 6060
\(\frac{9}{4}>\frac{4}{9}\)
\(\frac{18}{15}< \frac{23}{24}\)
\(\frac{18}{18}>\frac{28}{29}\)
\(\frac{13}{15}< \frac{3}{2}\)
a,
18:3=6 và (18.4):(3.4)=72:12=6
=>18:3=(18.4):(3.4)
b,81:9=9 và (81:3):(9:3)=27:3=9
=>81:9=(81:3):(9:3)
K mình nhé!
175,5
12x15-18:4
=180-4,5
=175,5