18 + 18 + 18 + 18 -27 -100000 =
1.Biểu thức (-13 + 18 - 27) sau khi bỏ ngoặc là:
13 + 18 - 27
-13 + 18 - 27
-13 - 18 - 27
13 + 18 + 27
b) 27 . 58 + 42 .27 d) 68 . 18 + 39 . 18 – 18 . 7
b) = 27.(58+42)
= 27.100=2700
d) =18.(68+39-7)
=18.100=1800
`b)`
`27.58 + 42.27`
`=27.(58+42)`
`=27.100`
`=2700`
`d)`
`68.18+39.18-18.7`
`=18.(68 + 39-7)`
`=18.100`
`=1800`
Áp dụng : `a.d + b.d = d.(a+d)`
b) 27.58+42.27=27.(58+42)=27.100=2700
d)68.18+39.18-18.7=18.(68+39-7)=18.100=1800
bài 2: rút gọn rồi tính
a) 8/5 -18/27 =.................................................. .................................................. b)12/20-6/18............................................ c)18/21-12/27...................................... d)8/12-20/50................................................. |
|
a: =8/5-2/3=24/15-10/15=14/15
12/20-6/18=3/5-1/3=9/15-5/15=4/15
b: 18/21-12/27=6/7-7/9=54/63-49/63=5/63
8/12-20/50=2/3-2/5=10/15-6/15=4/15
\(a,\dfrac{8}{5}-\dfrac{18}{27}=\dfrac{8}{5}-\dfrac{2}{3}=\dfrac{14}{15}\\ \dfrac{12}{20}-\dfrac{6}{18}=\dfrac{3}{5}-\dfrac{1}{3}=\dfrac{4}{15}\\ b,\dfrac{18}{21}-\dfrac{12}{27}=\dfrac{6}{7}-\dfrac{4}{9}=\dfrac{26}{63}\\ \dfrac{8}{12}-\dfrac{20}{50}=\dfrac{2}{3}-\dfrac{2}{5}=\dfrac{4}{15}\)
a) 8/5 -18/27 = 8/5 - 2/3 = 14/15 12/20 - 6/18 = 3/5 - 1/3 = 4/15 b) 18/21 - 12/27 = 6/7 - 4/9 = 26/63 8/12 - 20/50 = 2/3 - 2/5 = 4/15 |
Câu 15: Tìm x thuộc bội của 9 và x < 63
A. x ∈ {0; 9; 18; 27; 36; 45; 54} B. x ∈ {0; 9; 18; 28; 35}
C. x ∈ {9; 18; 27; 36; 45; 54; 63} D. x ∈ {9; 18; 27; 36; 45; 55; 63}
Tính nhanh
41/27 × 13/18 -13/18 × 14/27
41/27*13/18-13/18*14/27
41/27* 0 *14/27=
0 *14/27=0
A= 90/15*18+90/18*21+90/21*24+90/24*27+90/27*30
Tính nhẩm:
18 : 9 =
27 : 9 =
36 : 9 =
45 : 9 =
18 : 2 =
27 : 3 =
36 : 4 =
45 : 5 =
18 : 9 = 2
27 : 9 = 3
36 : 9 = 4
45 : 9 = 5
18 : 2 = 9
27 : 3 = 9
36 : 4 = 9
45 : 5 = 9
Tinh bang cach thuan tien :
41 / 27 x 13 / 18 - 13 / 18 x 14 / 27
41 / 27 x 13 / 18 - 13 / 18 x 14 / 27 = ( 41 / 27 - 14 / 27 ) x 13 / 18 = 27 / 27 x 13 / 18 = 1 x 13 / 18 = 13 / 18