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a)2/3x4/7=8/21
b)8/21:2/3=8/21x3/2=24/42=4/7
c)8/21:4/7=8/21x7/4=56/85=7//12
d)4/7X2/3=8/21
3/11x2=6/11
6/11:3/11=2
6/11:2=3/11
2x3/11=6/11
tk mk nha
3 / 11 x 2 = 6 /11
6 /11 x 3/11 = 6/3
6 / 11: 2 = 12/11
2x 3/11 = 6/11
A. \(\frac{2}{5}\div\frac{2}{3}=\frac{2}{5}\times\frac{3}{2}=\frac{2\times3}{5\times2}=\frac{3}{5}\text{ }\)
B. \(\frac{4}{7}\div\frac{4}{5}=\frac{4}{7}\times\frac{5}{4}=\frac{4\times5}{7\times4}=\frac{5}{7}\)
C. \(\frac{1}{6}\div\frac{1}{3}=\frac{1}{6}\times\frac{3}{1}=\frac{3}{6}=\frac{1}{2}\)
D. \(\frac{1}{4}\div\frac{1}{8}=\frac{1}{4}\times\frac{8}{1}=\frac{8}{4}=2\)
1, Rút gọn rồi tính
a) \(\frac{4}{5}+\frac{3}{15}\)
= \(\frac{4}{5}+\frac{1}{5}\)
= \(\frac{5}{5}\)
= \(1\)
b) \(\frac{2}{3}+\frac{32}{24}\)
= \(\frac{2}{3}+\frac{4}{3}\)
= \(\frac{6}{3}\)
= \(2\)
c) \(\frac{5}{6}+\frac{15}{18}\)
= \(\frac{5}{6}+\frac{5}{6}\)
= \(\frac{10}{6}\)
= \(\frac{5}{3}\)
2, Tính rồi rút gọn
a) \(\frac{8}{15}+\frac{2}{3}\)
= \(\frac{8}{15}+\frac{10}{15}\)
= \(\frac{18}{15}\)
= \(\frac{6}{5}\)
b) \(\frac{3}{7}+\frac{4}{8}\)
= \(\frac{24}{56}+\frac{28}{56}\)
= \(\frac{52}{56}\)
= \(\frac{13}{14}\)
1-2+3-4+5-6+.....+99-100+101.
Ta viết lại tổng như sau:
101 - 100 + 99 - 98 + ... + 5 - 4 + 3 - 2 + 1
1 + 1 + ... + 1 + 1 + 1
Số phép trừ trong dãy tính là:
( 101 - 1 ) : 2 = 50 ( phép trừ )
Kết quả dãy số là:
1 x 50 + 1 = 51
Vậy: 1-2+3-4+5-6+.....+99-100+101.
= 51
\(\frac{3}{4}+\frac{1}{6}=\frac{9+2}{12}=\frac{11}{12}\)
\(\frac{11}{12}-\frac{3}{4}=\frac{11-9}{12}=\frac{2}{12}=\frac{1}{6}\)
\(\frac{11}{12}-\frac{1}{6}=\frac{11-2}{12}=\frac{9}{12}=\frac{3}{4}\)
\(\frac{1}{6}+\frac{3}{4}=\frac{2+9}{12}=\frac{11}{12}\)
1-2+3-4+5-6+...+99-100+101
= (1+3+5+...+101) - (2+4+6+...+100)
tu 1 den 101 co : (101-1):2+1=51
1+..+101 = (1+101)x 51:2= 2601
tu 2 den 100 co : (100-2);2+1=50
2+...+100 = (100 +2) x 50:2=2550
=> A= 2601-2550=51
học tốt
a) 2/5 + 1/2 + 7/10
= 4/10 + 5/10 + 7/10
= 9/10 + 7/10
= 16/10 = 8/5
b) 4/9 + 11/8 - 5/6
= 32/72 + 99/72 - 60/72
= 191/72
c) 9/20 - 8/15 x 5/12
= 9/20 - 2/9
= 41/180
d) 2/3 : 4/5 : 7/12
= 5/6 : 7/12
= 10/7
4x2/7=8/7
8/7:2/7=8/7x7/2=4
8/7:4=8/7x1/4=2/7
2/7x4=1/14
4 x \(\frac{2}{7}\) = \(\frac{4x2}{7}\) = \(\frac{8}{7}\)
\(\frac{8}{7}\) : \(\frac{2}{7}\) = \(\frac{8}{7}\) x \(\frac{7}{2}\) = \(\frac{8x7}{7x2}\) = \(\frac{56}{14}\) = 4
\(\frac{8}{7}\) : 4 = \(\frac{8}{7x4}\) = \(\frac{8}{28}\) = \(\frac{2}{7}\)
\(\frac{2}{7}\) x 4 = \(\frac{2x4}{7}\) = \(\frac{8}{7}\)
tk mk nhé lưu kim linh
ai thấy đúng thì tk mk nha
cảm ơn các bn