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b, 3/5 + 4/7 + 2/8 + 10/25 + 9/21 + 28/16
= 3/5 + 4/7 + 2/8 + 2/5 + 3/7 + 14/8
= (3/5 + 2/5) + ( 4/7 + 3/7) + ( 2/8 + 14/8)
= 1 + 1 + 7/4
= 2 + 7/4 = 15/4
c , 8/7 + 7/6 + 5/8 + 10/12 + 24/28 + 6/16
= c , 8/7 + 7/6 + 5/8 + 5/6 + 6/7 + 1/2
= (8/7 + 6/7) + (7/6 + 5/6) + 5/8 + 1/2
= 14/7 + 12/6 + 5/8 + 1/2
= 2 + 2 + 5/8 + 1/2
= 4 + 9/8 = 41/8
a) \(A=\frac{27\text{x}45+27\text{x}25}{2+4+6+8+...+18}=\frac{27\left(45+25\right)}{\left(18+2\right)\text{x}\left(\frac{18-2}{2}+1\right)}\)
\(A=\frac{27\text{x}70}{20\text{x}9}=\frac{3\text{x}9\text{x}10\text{x}7}{10\text{x}2\text{x}9}\)
\(A=\frac{21}{2}\)
b) \(B=\frac{28\text{x}108-52\text{x}12}{32-28+24-20+16-12+8-4}\)
\(B=\frac{28\text{x}12\text{x}9\text{}\text{}-52\text{x}12}{\left(32-28\right)+\left(24-20\right)+\left(16-12\right)+\left(8-4\right)}\)
\(B=\frac{12\left(28\text{x}9-52\right)}{4+4+4+4}=\frac{12\text{x}200}{4\text{x}4}\)
\(B=\frac{4\text{x}3\text{x}4\text{x}50}{4\text{x}4}=150\)
a) \(\frac{2}{5}+\frac{9}{15}=\frac{2}{5}+\frac{3}{5}=\frac{5}{5}=1\)
b) \(\frac{15}{45}+\frac{25}{30}=\frac{1}{3}+\frac{5}{6}=\frac{2}{6}+\frac{5}{6}=\frac{7}{6}\)
c) \(\frac{28}{32}+\frac{45}{72}=\frac{7}{8}+\frac{5}{8}=\frac{12}{8}=\frac{3}{2}\)
d) \(\frac{8}{28}+\frac{5}{30}=\frac{2}{7}+\frac{1}{6}=\frac{12}{42}+\frac{7}{42}=\frac{19}{42}\)
a) \(\frac{2}{5}+\frac{9}{15}\)=\(\frac{2}{5}+\frac{3}{5}=\frac{2+3}{5}=1\)
b)\(\frac{15}{45}+\frac{25}{30}=\frac{1}{3}+\frac{5}{6}=\frac{2}{6}+\frac{5}{6}=\frac{2+5}{6}=\frac{7}{6}\)
c)\(\frac{28}{32}+\frac{45}{72}=\frac{7}{8}+\frac{5}{8}=\frac{7+5}{8}=\frac{12}{8}=\frac{3}{2}\)
d)\(\frac{8}{28}+\frac{5}{30}=\frac{2}{7}+\frac{1}{6}=\frac{12}{42}+\frac{7}{42}=\frac{12+7}{42}=\frac{19}{42}\)
a) 2/5+9/5=11/5
b) 15/45+25/30=7/6
c) 28/32+45/72=3/2
d) 8/28+5/30=19/42
bài 2
a) x - 4/5 =4/5 + (3/7+3/5)
x-4/5=4/5+36/35
x-4/5=64/35
x=64/35+4/5
x=92/35
b) x-7/35=4/5
x=4/5+7/35
x=1
nhớ tk m nhé
a = 18/5
b = 3/9 + 5/6 = 6/18 + 25/18 = 31/18
c = 7/8 + 5/8 = 12/8
d = 4/14 + 1/6 = 14/42 + 7/42 = 21/42 -= 7/14
b2
x - 4/5 = 4.5 + ( 3/7 + 3/5 )
x - 4/5 = 49/35
x = 49/35 + 4/5
x = 77/35
x - 7/35 = 4/5
x = 4/5 + 7/35
x = 1
mình ko chắc chắn đâu
mình nghĩ mình làm sai
Câu 1:Tính hợp lí
a) 28.72+28.28
=28.(72+28)
=28.100
= 2800
b)50.5.2
=50.2.5
=100.5
= 500
Câu 2:Tìm x
a) 3x+6=15
3x =15-6
3x = 9
x = 9:3
x = 3
b)100-(4x+8):10=8
100-(4x+8) =8.10
100-(4x+8) = 80
4x+8 = 100-80
4x+8 = 20
4x = 20-8
4x = 12
x = 12:4
x = 3
K cho mk nhé!!!!!Thanks>_<
câu 1
a )
28x72+28x28
=28+72
=100
b )
50x5x2
=50x10
=500
câu 2
a )
3x+6=15
3x=15-6
3x=9
x=9:3
x=3
b)
100-(4x+8):10=8
100-(4x+8=)8x10
100-(4x+8)=80
4x+8=100-80
4x+8=20
4x=20-8
4x=12
x=12:4
x=3
a và d là hai phương án sai
vì 28-12:8=28-1,5=26,5>4
và 24:2,3>4
a) \(\frac{1}{4}\)
b) \(\frac{2}{7}\)
c) \(\frac{2}{3}\)
a)25/50 + 5/15 = 1/2 + 1/3 = 5/6
b)72/90 + 7/28 = 4/5 + 1/4 =\(1\frac{1}{20}\)
c)32/96 + 8/28 = 1/3 + 2/7 = 13/21
Chúc bạn tết vui vẻ nha!
\(\frac{25}{50}+\frac{5}{15}=\frac{1}{2}+\frac{1}{3}=\frac{3}{6}+\frac{2}{6}=\frac{5}{6}\)
\(\frac{72}{90}+\frac{7}{28}=\frac{8}{10}+\frac{1}{4}=\frac{32}{40}+\frac{10}{40}=\frac{42}{40}=\frac{21}{20}\)
\(\frac{32}{96}+\frac{8}{28}=\frac{1}{3}+\frac{2}{7}=\frac{7}{21}+\frac{6}{21}=\frac{13}{21}\)
Đáp án B