a]1/3 + 3/4 - 7/12
b]6/11 chia 5/22 -4/5
c]5/18 nhân 8
d]7/15 chia 5
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`a) 5 / 13 xx 4 / 15 xx 13 = [ 5 xx 4 xx 13 ] / [ 13 xx 5 xx 3 ] = 4 / 3`
`b) ( 3 / 7 + 5 / 2 ) xx 7 / 5 = 3 / 7 xx 7 / 5 + 5 / 2 xx 7 / 5 = 3 / 5 + 7 / 2 = 6 / 10 + 35 / 10 = 41 / 10`
`c) 1 / 5 xx 11 / 18 + 11 / 18 xx 3 / 5 = 11 / 18 xx ( 1 / 5 + 3 / 5 ) = 11 / 18 xx 4 / 5 = [ 11 xx 2 xx 2 ] / [ 2 xx 9 xx 5 ] = 22 / 45`
\(a,\dfrac{5}{13}\times\dfrac{4}{15}\times13=\dfrac{4}{3}\)
\(b,\left(\dfrac{3}{7}+\dfrac{5}{2}\right)\times\dfrac{7}{5}=\left(\dfrac{6}{14}+\dfrac{35}{14}\right)\times\dfrac{7}{5}=\dfrac{41}{14}\times\dfrac{7}{15}=\dfrac{41}{30}\)
\(c,\dfrac{1}{5}\times\dfrac{11}{18}+\dfrac{11}{18}\times\dfrac{3}{5}=\dfrac{11}{18}\times\left(\dfrac{1}{5}+\dfrac{3}{5}\right)=\dfrac{11}{18}\times\dfrac{4}{5}=\dfrac{22}{45}\)
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
Bài 2:
Sau 2 giờ con ốc sên bò được:
1/5+1/6=11/30(cây cột)
Sau 2 giờ thì con ốc sên còn phải bò:
1-11/30=19/30(cây cột)
a) chứng tỏ : abcabc chia hết cho 11
Ta có 123123:11=11193
Vậy abcabc chia hết cho 11
b)\(\frac{9\cdot15\cdot21\cdot12\cdot20}{5\cdot6\cdot45\cdot18\cdot4}=\frac{9\cdot3\cdot5\cdot3\cdot7\cdot2\cdot2\cdot3\cdot2\cdot2\cdot5}{5\cdot2\cdot3\cdot5\cdot3\cdot3\cdot2\cdot3\cdot3\cdot2\cdot2}\)\(=\frac{7\cdot5}{3}=\frac{35}{3}\)
\(\frac{2}{3}\)x \(\frac{5}{8}\)x \(\frac{8}{15}\)= \(\frac{2}{3}\)x \(\frac{1}{15}\)= \(\frac{2}{45}\)
\(\frac{22}{5}\)x \(12\)x \(\frac{20}{40}\)= \(\frac{22}{5}\)x \(12\)x \(\frac{1}{2}\)= \(\frac{22}{5}\)x 6 = \(\frac{122}{5}\)
\(\frac{7}{2}\)x \(\frac{26}{7}\)x \(\frac{4}{13}\)= \(\frac{91}{7}\)x \(\frac{4}{13}\)
a) 4/7 + 9/11
= 44/77 + 63/ 77
= 107/77
b) 11/12 * 6/9 - 3/8
= 66/108 - 3/8
= 11/18 - 3/8
= 44/72 - 27/72
= 17/72
c) 5/7 : 9/14 -17/18
= 5/7 * 14/9 - 17/18
= 70/63 - 17/18
= 10/9 - 17/18
= 20/18 - 17/18
= 3/18
= 1/6
OK
a) 1/3 + 3/4 - 7/12
= 4/12 + 9/12 - 7/12
= 6/12
= 1/2
b) 6/11 : 5/22 - 4/5
= 6/11 * 22/5 - 4/5
= 12/5 - 4/5
= 8/5
c) 5/18 * 8
= 40/18
= 20/9
d) 7/15 : 5
= 7/15 * 1/5
= 7/75
OK
a, \(\frac{1}{3}+\frac{3}{4}-\frac{7}{12}\)
= \(\frac{13}{12}-\frac{7}{12}\)
= \(\frac{1}{2}\)
\(b,\frac{6}{11}:\frac{5}{22}-\frac{4}{5}\)
= \(\frac{12}{5}-\frac{4}{5}\)
\(=\frac{8}{5}\)
\(c,\frac{5}{18}x8\)
=\(\frac{20}{9}\)
\(d,\frac{7}{15}:5\)
= \(\frac{7}{15}x\)\(\frac{1}{5}\)
\(=\frac{7}{75}\)