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\(\left(\dfrac{135}{2371}+\dfrac{24}{25}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{3}-\dfrac{1}{6}\right)\)
\(=\left(\dfrac{135}{2371}+\dfrac{24}{25}\right)\times\left(\dfrac{3}{6}-\dfrac{2}{6}-\dfrac{1}{6}\right)\)
\(=\left(\dfrac{135}{2371}+\dfrac{24}{25}\right)\times0=0\)
muốn tính nhanh bài này ta chỉ việc lấy 1/2-1/3-1/6=0
số nào nhân với 0 cũng bằng 0
vậy phép tinh này bằng 0
25/7 - 2 + 3/2 = 43/14
4/5 x 10/3 : 8= 4/5 x 10/3 x 1/8 = 1/3
7/3 + 2/5 : 1/6 = 7/3+ 2/5 x 6 = 7/3 + 12/5 = 71/15
b)1/2*2/3*3/4*4/5*5/6*6/7*7/8*8/9*9/10
=1x2x3x4x5x6x7x8x9
2x3x4x5x6x7x8x9x10
= 1
10
`a, 4/9 + 2/5 + 5/9= (4/9 +5/9) + 2/5= 1 + 2/5= 5/5 + 2/5= 7/5`
`b, 6/13 + 5/8 + 7/13=(6/13 + 7/13) + 5/8=1+5/8= 8/8 + 5/8= 13/8`
`c, 5/11 + 6/25 + 66/121 = ( 5/11 + 66/121 ) + 6/25=1 + 6/25 = 25/25 + 6/25 = 31/25`
`d, 1/2 + 1/3 + 1/4 + 1/6 + 1/12 + 1/24= (1/2 + 1/4) +(1/3 + 1/6) + (1/12 + 1/24)= 3/4 + 1/2 + 1/8= 6/8 + 4/8 + 1/8= 11/8`
`@ yl`
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) \(15400:x=25\)
\(\Rightarrow x=15400:25\)
\(\Rightarrow x=616\)
b) \(\left(x+3\right):247=675:135\)
\(\Rightarrow\left(x+3\right):247=5\)
\(\Rightarrow x+3=5\times247\)
\(\Rightarrow x+3=1235\)
\(\Rightarrow x=1235-3\)
\(\Rightarrow x=1232\)
c) \(1224:\left(x-8\right)=24\)
\(\Rightarrow\left(x-8\right)=1224:24\)
\(\Rightarrow x-8=51\)
\(\Rightarrow x=51+8\)
\(\Rightarrow x=59\)
rất be like =)
lớp 4:)?