2/3x5+3/5x8+11/8x19+13/19x32+25/32x57+30/57x87
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2/3x5+3/5x8+11/8x19+13/19x32+25/32x57+30/57x87
\(\frac{2}{3.5}+\frac{3}{5.8}+\frac{11}{8.19}+\frac{13}{19.32}+\frac{25}{32.57}+\frac{30}{57.87}\)
=\(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{19}+\frac{1}{19}-\frac{1}{32}+\frac{1}{32}-\frac{1}{57}+\frac{1}{57}-\frac{1}{87}\)
= 1/3 - 1/87
= 28/87
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a) Cho b = 1/3 + 1/16 + 1/19 + 1/21 + 1/61 + 1/72 + 1/83 + 1/94.
So sánh B với 3/5
b) Tính nhanh:
A = 2/3x5 + 3/5x8 +11/8x19 + 13/19x32 + 25/32x57 + 30/57x87
Mình đang cần gấp!!!!
a,Ta có :
1/3 + 1/16 + 1/19 + 1/21 + 1/61 + 1/72 + 1/83 + 1/94 = 0,54
3/4 = 0,6
=>b < 3/4
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A=2/3x5+3/5x8+11/8x9+13/9x32+25/32x57+30/57x87
câu 2.Tính bằng cách thuận tiện nhất( mẫu 3)
7/8x9/5x8/3x5
`7/8xx9/5xx8/3xx5=[7xx3xx3xx8xx5]/[8xx5xx3]=7xx3=21`
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\(=\dfrac{7\times3\times3\times8\times5}{8\times5\times3}=\dfrac{21}{1}=21\)
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Bài 1: Thực hiện phép tính:
1, 4/23 + 5/21 + 0,5 - 4/23 + 16/21
2, (1/3 + 12/67 + 13/41)-(79/67 - 28/41)
3, 12,5 x (-5/7)+1,5 x (-5/7)
4, 3/8x19 1/3- 3/8x33 1/3
5, 5/7x(-3/11)+5/7x(-8/11)+2 5/7
6, (-5/11:13/8-5/11:13/5)- giá trị tuyệt đối của -1/33
1: \(\dfrac{4}{23}+\dfrac{5}{21}+\dfrac{1}{2}-\dfrac{4}{23}+\dfrac{16}{21}\)
\(=1+\dfrac{1}{2}\)
\(=\dfrac{3}{2}\)
2: \(\left(\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}\right)-\left(\dfrac{79}{67}-\dfrac{28}{41}\right)\)
\(=\dfrac{1}{3}+\dfrac{12}{67}+\dfrac{13}{41}-\dfrac{79}{67}+\dfrac{28}{41}\)
\(=\dfrac{1}{3}\)
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\(\frac{2}{3.5}+\frac{3}{5.8}+\frac{11}{8.19}+\frac{13}{19.32}+\frac{25}{32.57}+\frac{30}{57.87}\)\(\frac{2}{3.5}+\frac{3}{5.8}+\frac{11}{8.19}+\frac{13}{19.32}+\frac{25}{32.57}+\frac{30}{57.87}\)
\(\frac{2}{3.5}+\frac{3}{5.8}+\frac{11}{8.19}+\frac{13}{19.32}+\frac{25}{32.57}+\frac{30}{57.87}\)
\(=\frac{5-3}{3.5}+\frac{8-5}{3}+\frac{19-8}{8.19}+\frac{32-29}{19.32}+\frac{57-32}{32.57}+\frac{87-57}{57.87}\)
\(=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{19}+\frac{1}{19}-\frac{1}{32}+\frac{1}{32}-\frac{1}{57}+\frac{1}{57}-\frac{1}{87}\)
\(=\frac{1}{3}-\frac{1}{87}=\frac{28}{87}\)
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Tính
a)S1=2/3x5+2/5x7+2/7x9+...+2/97x99
b)S2=6/2x5+6/5x8+6/8x11+...+6/29x32
b)
S2=6/2x5+6/5x8+6/8x11+...+6/29x32
=2.(3/2.5+3/5.8+...+3/29.32)
=2.(1/2-1/5+1/5-1/8+...+1/29-1/32)
=2.(1/2-1/32)
=2.15/32
=15/16
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a)
Ta có:
S1=2/3x5+2/5x7+2/7x9+...+2/97x99
=1/3-1/5+1/5-1/7+...+1/97-1/99
=1/3-1/99
=32/99
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b)
S2=6/2x5+6/5x8+6/8x11+...+6/29x32
=2.(3/2.5+3/5.8+...+3/29.32)
=2.(1/2-1/5+1/5-1/8+...+1/29-1/32)
=2.(1/2-1/32)
=2.15/32
=15/16
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a)
Ta có:
S1=2/3x5+2/5x7+2/7x9+...+2/97x99
=1/3-1/5+1/5-1/7+...+1/97-1/99
=1/3-1/99
=32/99
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0,75-(13/11-50%):5/11
A=1/6+1/12+1/20+1/30+1/42+1/56+1/72
B=2/1x3+2/3x5+2/5x7+...+2/49x51
Dấu / là phần nha. Giúp mik với đang cần gấp!!!
A=1/6+1/12+1/20+1/30+1/42+1/56+1/72
A=1/2*3+1/3*4+1/4*5+1/5*6+1/6*7+1/7*8+1/8*9
A=1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9
A=1/2-1/9
Câu B tương tự nha bạn :333
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tính nhanh
(8x7-16-5x8)x (1+2+3+4+5+6+7+8+9)
1+3+5+7+9+11+13+15+17+19
(8 x 7 - 16 - 5 x 8) x (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9)
= [8 x 7 - 8 x 2 - 5 x 8] x [(1 + 9) + (2 + 8 ) + (3 + 7) + (4 + 6) + 5]
= [8 x (7 - 2 - 5)] x [10 + 10 + 10 + 10 + 10 + 5]
= (8 x 0) x 45
= 0
1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19
= (1 + 9) + (3 + 7) + (5 + 15) + (11 + 19) + (13 + 17)
= 10 + 10 + 20 + 30 + 30
= 100
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