Tính nhanh
3 * 72* 8 + 4 * 6 * 12 + 2 * 16 * 12
tính nhanh :
2/9 + 6/27 + 8/36 +12/54 + 16/72 + 18/81
Tính nhanh tổng sau:
2/9 + 6/27 + 8/36 + 12/54 + 16/72 + 18/81
2/9 + 6/27 + 8/36 + 12/54 + 16/72 + 18/81=\(\frac{2}{9}+\frac{2}{9}+\frac{2}{9}+\frac{2}{9}+\frac{2}{9}+\frac{2}{9}\) = \(\frac{2}{9}\). 6 = \(\frac{12}{9}\)= \(\frac{4}{3}\)
\(\frac{2}{9}+\frac{6}{27}+\frac{8}{36}+\frac{12}{54}+\frac{16}{72}+\frac{18}{81}\)
\(=\frac{2}{9}+\frac{2}{9}+\frac{2}{9}+\frac{2}{9}+\frac{2}{9}+\frac{2}{9}\)
\(=\frac{2}{9}×6=\frac{4}{3}\)
tính nhanh hộ mình 2 câu này với :
1*2+2*4+3*6+4*8+5*10 / 3*4+6*8+9*12+12*16+15*20
2*4+2*4*8+4*8*16+8*16*32 / 3*4+2*6*8+4*12*168*24*32
a)
\(\frac{1.2+2.4+3.6+4.8+5.10}{3.4+6.8+9.12+12.16+15.20}\)
\(\frac{2.3\left(1.2\right)+2.3\left(2.4\right)+2.3\left(3.6\right)+2.3\left(4.8\right)+2.3\left(5.10\right)}{3.4\left(3.4+6.8+9.12+12.16+15.20\right)}\)
\(=\frac{\left(3.4+6.8+9.12+12.16+15.20\right)}{2.3\left(3.4+6.8+9.12+12.16+15.20\right)}=\frac{1}{2.3}=\frac{1}{6}\)
Tính nhanh
2×169×12-3×68×8-24
2×56×24-3×36×16+4×12×95-6×3×8×5
\(2\times169\times12-3\times68\times8-24\)
\(=24\times169-24\times68-24\)
\(=24\times\left(169-68-1\right)\)
\(=24\times100=2400\)
tính nhanh
2/8 * 3/12 + 4/16 * 6/24
=1/4 x 1/4 + 1/4 x 1/4 ( rút gọn)
= 1/16 + 1/16
= 2/16
k mk nha . cảm ơn bạn nhìu
\(\frac{2}{8}.\frac{3}{12}+\frac{4}{16}.\frac{6}{24}\)
\(=\frac{2}{8}.\frac{3}{12}+\frac{4}{16}.\frac{3}{12}\)
\(=\frac{3}{12}.\left(\frac{2}{8}+\frac{4}{16}\right)\)
\(=\)\(\frac{3}{12}.\frac{1}{2}\)
\(\frac{1}{8}\)
Tính nhanh a) 6*7*8*9/18*16*14*12 b) 4*15*9*24/3*12*8*25
a: =6/12*7/14*8/16*9/18=1/2*1/2*1/2*1/2=1/16
b: =4/12*15/3*9/25*24/8
=1/3*3*5*9/25=9/5
1) 15 - 98 + 91 - 75 + 98 - 91 - 13
2) 5 - ( 4 - 7 + 12 ) + ( 4 - 7 + 12 ) - 10
3) 20 - ( 25 - 98 + 12 ) + ( 25 - 98 - 72 )
4) - ( 17 - 4 + 13 + | -17 | + 13 )
5) | -16 | - ( 5 - 8 + 7) - ( - 5 ) - 8
6) -20 + ( 3 - 16 + 7 ) - ( 3 - 16 + 7 )
7) 32 - ( 5 - 8 + 32 ) + ( 5 - 8 + 6 )
8) -20 - ( 25 - 11 + 8 ) + ( 25 - 8 + 20 )
1)-73
2)-5
3)-64
4)-56
5)9
6)-20
7)6
8)-2
Tick nha
đăng tùng câu một thui bạn
bạn làm thế chắc tụi mk xỉu gần hết
1/ Tính nhanh:
a. 5/7×5/11+5/11×2/9-5/7×17/11
b. 1×2+2×4+3×6+4×8+5×10/3×4+6×8+9×12+12×16+15×20
coi lại câu a
1.1+1.1+1.1+1.1+1.1/1.1+1.1+9.3+6.8+.2
Tính nhanh:
a) 2/9+6/27+8/36+12/54+16/72+18/81
b) ( 1-2/5) * ( 1-2/7 ) * ( 1-2/9 ) *.....................( 1-2/99)
c) Tính tổng sau bằng cách hợp lí và nhanh nhất
1/2+1/4+1/8+1/16+........................+1/1024
Giúp mik nha các bạn, mik đang cần lắm đó!
a)
Vì 2/9=6/27=8/36=12/54=16/72=18/81 nên:
2/9+6/27+8/36+12/54+16/72+18/81=
2/9+2/9+2/9+2/9+2/9+2/9=
2/9*6=
12/9=
4/3
Vậy 2/9+6/27+8/36+12/54+16/72+18/81=4/3
b)
Ta có:
1-2/5=3/5
1-2/7=5/7
1-2/9=7/9
...
1-2/99=97/99
Vậy (1-2/5)*(1-2/7)*(1-2/9)*...*(1-2/99)=
3/5*5/7*7/9*...*97/99=
(3*5*7*...*97)/(5*7*9*...*99)=
3/99=
1/33
Vậy (1-2/5)*(1-2/7)*(1-2/9)*...*(1-2/99)=1/33
c)
Gọi biểu thức 1/2+1/4+1/8+1/16+...+1/1024 là S,ta có:
S=1/2+1/4+1/8+1/16+...+1/1024
S*2=1+1/2+1/4+1/8+...+1/512
S*2-S=(1+1/2+1/4+1/8+...+1/512)-(1/2+1/4+1/8+1/16+...+1/1024)
S=1-1/1024
S=1023/1024
Vậy 1/2+1/4+1/8+1/16+...+1/1024=1023/1024