Chó

=(84,35- 19,35) + (32,18 - 27,18)

=65+5

=70

\(\dfrac{1}{10}+\dfrac{4}{20}+\dfrac{9}{30}+\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
\(=\dfrac{1}{10}+\dfrac{1}{5}+\dfrac{3}{10}+\dfrac{2}{5}+\dfrac{1}{2}+\dfrac{3}{5}+\dfrac{7}{10}+\dfrac{4}{5}+\dfrac{9}{10}\)
\(=\left(\dfrac{1}{10}+\dfrac{3}{10}+\dfrac{7}{10}+\dfrac{9}{10}\right)+\left(\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}\right)+\dfrac{1}{2}\)
\(=2+2+\dfrac{1}{2}\)
\(=4+\dfrac{1}{2}\)
\(=\dfrac{8}{2}+\dfrac{1}{2}=\dfrac{9}{2}\)

(72,18-82,18):X=2,5

40:X=2,5

X=40:2,5

X=16

bài này dễ mà bạn tự tính đi

72,18:x-32,18:x=2,5

(72,18-31,18):x=2,5

41:x=2,5

x=41:2,5

x=16,4

\(\frac{1}{10}+\frac{4}{20}+\frac{9}{30}+\frac{16}{40}+\frac{25}{50}\) \(+\frac{36}{60}+\frac{49}{70}+\frac{64}{80}+\frac{81}{90}\)

\(=\frac{1}{10}+\frac{1}{5}+\frac{3}{10}+\frac{2}{5}+\frac{1}{2}+\frac{3}{5}+\frac{7}{10}+\frac{4}{5}+\frac{9}{10}\)

\(=\left(\frac{1}{10}+\frac{9}{10}\right)+\left(\frac{1}{5}+\frac{4}{5}\right)+\left(\frac{3}{10}+\frac{7}{10}\right)+\left(\frac{2}{5}+\frac{3}{5}\right)+\frac{1}{2}\)

\(=1+1+1+1+0,5\)

\(=4+0,5\)

\(=4,5\)

(   56 × 49   ) ÷ 7 =   7 × 8 × 7 × 7 ÷ 7 = 7 × 8 × 7 × 7 ÷ 7 = 7 × 8 × 7 = 392

49 x 50 + 13 x 49 + 49

= 49 x ( 50 + 13 + 1 )

= 49 x 64

= 3136

Học tốt !!! ~

   49 x 50 + 13 x 49 + 49 

= 49 x 50 + 13 x 49 + 49 x 1 

= 49 x ( 50 + 13 + 1 )

= 49 x 64

= 3136

k mình nha

hihihiihihihihihihihihihihihihiihihihihihihiihihihihihihiihihihihih

=125x8=1000

=125x8=1000

( 56 x 49) : 7

= 56 : 7 x 49

= 8 x 49

= 8 x (50 - 1)

= 8 x 50 - 8 x 1

= 400 - 8

= 392