2x8=
3x9=
4x5=
5x6=
20x4=
30x3=
12:2=
12:3=
2x9=
5x7=
90:3=
40:2=
18:3=
30x2=
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2 x 1 = 2 | 3 x 1 = 3 | 4 x 1 = 4 | 5 x 1 = 5 |
2 x 2 = 4 | 3 x 2 = 6 | 4 x 2 = 8 | 5 x 2 = 10 |
2 x 3 = 6 | 3 x 3 = 9 | 4 x 3 = 12 | 5 x 3 = 15 |
2 x 4 = 8 | 3 x 4 = 12 | 4 x 4 = 16 | 5 x 4 = 20 |
2 x 5 = 10 | 3 x 5 = 15 | 4 x 5 = 20 | 5 x 5 = 25 |
2 x 6 = 12 | 3 x 6 = 18 | 4 x 6 = 24 | 5 x 6 = 30 |
2 x 7 = 14 | 3 x 7 = 21 | 4 x 7 = 28 | 5 x 7 = 35 |
2 x 8 = 16 | 3 x 8 = 24 | 4 x 8 = 32 | 5 x 8 = 40 |
2 x 9 = 18 | 3 x 9 = 27 | 4 x 9 = 36 | 5 x 9 = 45 |
2 x 10 = 20 | 3 x 10 = 30 | 4 x 10 = 40 | 5 x 10 = 50 |
2x1=2 3x1=3 4x1=4 5x1=5 2:2= 1 3:3= 1 4:4=1 5:5=1
2x2= 4 3x2=6 4x2= 8 5x2=10 4:2= 2 6:3= 2 8:4=2 10:5=2
2x3=6 3x3= 9 4x3=12 5x3=15 6:2=3 9:3= 3 12:4=3 15:5=3
2x4=8 3x4=12 4x4=16 5x4=20 8:2=4 12:3=4 16:4=4 20:5=4
2x5=10 3x5= 15 4x5= 20 5x5= 25 10:2=5 15:3= 5 20:4=5 25:5=5
2x6=12 3x6=18 4x6= 24 5x6=30 12:2=6 18:3= 6 24:4=6 30:5=6
2x7= 14 3x7=21 4x7= 28 5x7=35 14:2=7 21:3=7 28:4=7 35:5=7
2x8=16 3x8=24 4x8= 32 5x8=50 16:2=8 24:3=8 32:4=8 40:5=8
2x9= 18 3x9= 27 4x9= 36 5x9=45 18:2=9 27:3= 9 36:9=9 45:5=9
2x10=20 3x10=30 4x10= 40 5x10=50 20:2=10 30:3=10 40:4= 10 50:5=10
=3.(1/1.2+1/2.3+....+1/9.10)+11.(1/2.9+1/9.16+...+1/93.100)
=3.(1-1/2+1/2-1/3+1/3 - ... - 1/10)+11.(1/2-1/9+1/9-...-1/100)
= 3.(1-1/10) + 11.( 1/2-1/100)
= 3. 9/10+11.49/100
chỗ này bạn tự tính máy tính nha
B=2/3x5 + 2/5x7 + 2/7x9 + ...+2/99x101
B= 1/3 - 1/5 + 1/5 - 1/7 + 1/7 -1/9 + ... + 1/99 - 1/101
B= 1/3 - 1/101
B=98/303
( k mk nhé ! Cách làm câu a và b của mk đều đúng 100% đấy ! Dạng này mk học từ lâu rồi ! )
\(\dfrac{7}{6}\) + \(\dfrac{5}{12}\) - \(\dfrac{1}{18}\) - 1
= \(\dfrac{42}{36}\) + \(\dfrac{15}{36}\) - \(\dfrac{2}{36}\) - \(\dfrac{36}{36}\)
= \(\dfrac{19}{36}\)
\(\dfrac{13}{6}\) + \(\dfrac{5}{18}+3-\dfrac{7}{12}\)
= \(\dfrac{78}{36}+\dfrac{10}{36}+\dfrac{108}{36}-\dfrac{21}{36}\)
= \(\dfrac{175}{36}\)
3 + \(\dfrac{11}{4}-\dfrac{1}{12}-\dfrac{3}{16}\)
= \(\dfrac{144}{48}+\dfrac{132}{48}-\dfrac{4}{48}-\dfrac{9}{48}\)
= \(\dfrac{263}{48}\)
\(\dfrac{2}{5}\) x \(\dfrac{7}{4}\) - \(\dfrac{2}{5}\) x \(\dfrac{3}{4}\)
= \(\dfrac{2}{5}\) x ( \(\dfrac{7}{4}\) - \(\dfrac{3}{4}\))
= \(\dfrac{2}{5}\) x \(\dfrac{4}{4}\)
= \(\dfrac{2}{5}\)
b1
a) \(\dfrac{1}{5.6}+\dfrac{1}{6.7}+\dfrac{1}{7.8}+\dfrac{1}{8.9}+\dfrac{1}{9.10}\)
\(=\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{10}\)
\(=\dfrac{1}{5}-\dfrac{1}{10}\)
\(=\dfrac{2}{10}-\dfrac{1}{10}\)
\(=\dfrac{1}{10}\)
b) \(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{99.100}\)
\(=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{99}-\dfrac{1}{100}\)
\(=\dfrac{1}{1}-\dfrac{1}{100}\)
\(=\dfrac{99}{100}\)
c) \(\dfrac{2}{3.5}+\dfrac{2}{5.7}+\dfrac{2}{7.9}+\dfrac{2}{9.11}\)
\(=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{11}\)
\(=\dfrac{1}{3}-\dfrac{1}{11}\)
\(=\dfrac{8}{33}\)
d) \(\dfrac{2}{3.5}+\dfrac{2}{5.7}+...+\dfrac{2}{99.101}\)
\(=\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{99}-\dfrac{1}{101}\)
\(=\dfrac{1}{3}-\dfrac{1}{101}\)
\(=\dfrac{98}{303}\)
2x8=16
3x9=27
4x5=15
5x6=30
20x4=80
30x3=90
12:2=6
12:3=4
2x9=18
5x7=35
90:3=30
40:2=20
18:3=6
30x2=90
16;27;20;30;80;90;6;4;18;35;30;20;6;60