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1/2+5/6+11/12+19/20+29/30+41/42+55/56+71/72+89/90 =
1-1/2+1-1/6+1-1/12+1-1/20+1-1/30+1-1/42+1-1/56+1-1/72+1-1/90 =
9 – (1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90) =
9 – [1/(1x2)+1/(2x3)+1/(3x4)+1/(4x5)+1/(5x6)+1/(6x7)+1/(7x8)+1/(8x9)+1/(9x10)] =
9 – ( 1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10) =
9 – (1 – 1/10) = 9 – 9/10 = 81/10
=(250-50)- (0,95x40)x(10x0,1)x(0,125x80)
=200 - (38 x1x10)
=200-380
=-180
tính đi nhé chẳng phải cái gì cũng nhờ vào máy là không được nhé
0,04 x 0,1 x 25 = (0,04 x 25) x 0,1 = 1 x 0,1 = 0,1
4,86 x 0,25 x 40 = 4,86 x (0,25 x 40) = 4,86 x 10 = 48,6
0,125 x 6,94 x 80 = (0,125 x 80) x (6,94) = 10 x 6,94 = 69,4
125 : 0,125 + 125 : 0,25 + 25 : 0,5
= 125 x 8+ 125x 4 + 25 x 2
=1000 + 500 + 50
= 1500 + 50
= 1550
3 x 15 + 21 x 15 + 85 x 5
= 45 + 315 + 425
= 785
15 - 30 + 40
= 25
21 + 19 - 50 + 10
= 0
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=-\dfrac{1}{20}+2\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{12}\times\dfrac{3}{12}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=-\dfrac{9}{20}\)
\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)
\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)
\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)
\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)
\(=\dfrac{44}{20}-\dfrac{5}{20}\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)
\(=\dfrac{6}{20}-\dfrac{15}{20}\)
\(=-\dfrac{9}{20}\)
a) (1,4 + 5,8) ; 3
= 7,2 : 3 = 2,4
b) (1,25 x 4 x 0,9) ; ( 9 x 5)
=(5 x 0,9) ; (9x 5 )
= 4,5 : 45
= 0,1
c) 2019 x 2 + 2019 x 8
= 2019 x ( 2 + 8)
= 2019 x 10
=20190
#chanh
a. 1,4 : 3 + 5,8 : 3
= (1,4 + 5,8) : 3
= 7,2 : 3
= 2,4
b. (1,25 x 3,6) : (9 x 5)
= 4,5 : 45
= 0,1
c. 2019 x 2 + 2019 : 0,125
= 2019 x 2 + 2019 x 8
= 2019 x (2 + 8)
= 2019 x 10 = 20190
18,69 x ( 3/5 -0,125 -19/40) = 0
giai han ra ban,mik bt dap an roi nhung ko bt cach tinh nhanh