a. 16 + (-6) =
b. 14 + (-6) =
c. (-8) + 12 =
Tính:
a) 16 + (-6)
b) 14 + (-6)
c) (-8) + 12
a) 16 + (–6) = 16 – 6 = 10;
b) 14 + (–6) = 14 – 6 = 8;
c) (–8) + 12 = 12 – 8 = 4.
Tính:
a) 16 + (– 26)
b) (– 15) + 4
c) 14 + (– 6)
d) (– 8) + 12
Tìm số nguyên x, biết:
a) (x-3) + 11 = -25
b) 5 - (x-1) =12 -16
c) (x-14) + (-22) -6 -12
d) (-15) - (15-x) = -6 + (-8)
Tính nhẩm:
7 + 6 8 + 4 6 + 8 9 + 7
13 - 7 12 - 8 14 - 6 16 - 9
13 - 6 12 - 4 14 - 8 16 - 7
tinh:a,16+(-6) b,14+(-6) c,(-8)+12
a,16+(-6)=+(16-6)=10
b,14+(-6)=+(14-6)=8
c,(-8)+12=+(12-8)=4
a ) 16 + ( - 6 ) =+ ( 16 - 6 ) =10
b ) 14 + ( - 6 ) = + ( 14 - 6 )= 8
c ) ( -8 ) +12 = - ( 12 - 8 ) = -4
TICK CHO MÌNH NHÉ !
Tính nhanh
a) 3 . ( 3/12 + -6/7 + 8/21 )
b)-2/3 . ( 2/18 + -6/12 - 3/33 )
c) 6/-14 + 4/25 +5/16 - (-3)/16
d) 4/-9 . ( 1/26 - 32/64 + (-4)/32 )
a: \(=3\cdot\left(\dfrac{1}{4}-\dfrac{6}{7}+\dfrac{8}{21}\right)\)
\(=3\cdot\left(\dfrac{21}{84}-\dfrac{72}{84}+\dfrac{32}{84}\right)\)
\(=\dfrac{-19}{28}\)
b: \(=\dfrac{-2}{3}\left(\dfrac{1}{9}-\dfrac{1}{6}-\dfrac{1}{11}\right)\)
\(=\dfrac{-2}{3}\cdot\dfrac{-29}{198}=\dfrac{29}{99\cdot3}=\dfrac{29}{297}\)
c: \(=\dfrac{-3}{7}+\dfrac{4}{25}+\dfrac{5}{16}+\dfrac{3}{16}\)
\(=\dfrac{-75+28}{175}+\dfrac{1}{2}\)
\(=\dfrac{-47}{175}+\dfrac{1}{2}=\dfrac{-94+175}{350}=\dfrac{81}{350}\)
d: \(=\dfrac{-4}{9}\cdot\left(\dfrac{1}{26}-\dfrac{1}{2}-\dfrac{1}{8}\right)\)
\(=\dfrac{-4}{9}\cdot\dfrac{-61}{104}=\dfrac{61}{26\cdot9}=\dfrac{61}{234}\)
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
Tính nhẩm:
14 − 9 = ..... | 16 − 7 = ..... | 12 − 8 = ..... | 6 + 9 = ..... |
8 + 8 = ..... | 11 − 5 = ..... | 13 − 6 = ..... | 18 − 9 = ..... |
14 − 6 = ..... | 17 − 8 = ..... | 12 − 5 = ..... | 3 + 9 = ..... |
9 + 4 = ..... | 11 − 9 = ..... | 3 + 8 = ..... | 16 − 8 = ..... |
Phương pháp giải:
Tính nhẩm các số rồi điền kết quả vào chỗ trống.
Lời giải chi tiết:
14 − 9 = 5 | 16 − 7 = 9 | 12 − 8 = 4 | 6 + 9 = 15 |
8 + 8 = 16 | 11 − 5 = 6 | 13 − 6 = 7 | 18 − 9 = 9 |
14 − 6 = 8 | 17 − 8 = 9 | 12 − 5 = 7 | 3 + 9 = 12 |
9 + 4 = 13 | 11 − 9 = 2 | 3 + 8 = 11 | 16 − 8 = 8 |
Tính nhẩm:
14 − 9 = ..... | 16 − 7 = ..... | 12 − 8 = ..... | 6 + 9 = ..... |
8 + 8 = ..... | 11 − 5 = ..... | 13 − 6 = ..... | 18 − 9 = ..... |
14 − 6 = ..... | 17 − 8 = ..... | 12 − 5 = ..... | 3 + 9 = ..... |
9 + 4 = ..... | 11 − 9 = ..... | 3 + 8 = ..... | 16 − 8 = ..... |
bài 2: tính nhanh :
a) 3/8 + 7/12 + 10/16 + 10/24 b) 4/6 + 7/13 + 17/9 + 19/13 + 1/9 + 14/6
c) 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56
a) \(\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{10}{16}+\dfrac{10}{24}\)
\(=\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{5}{8}+\dfrac{5}{12}\)
\(=\left(\dfrac{3}{8}+\dfrac{5}{8}\right)+\left(\dfrac{7}{12}+\dfrac{5}{12}\right)\)
\(=1+1\)
\(=2\)
b) \(\dfrac{4}{6}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{14}{6}\)
\(=\dfrac{2}{3}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{7}{3}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)
\(=3+2+2\)
\(=7\)
c) \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)
\(=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)
\(=1-\dfrac{1}{7}\)
\(=\dfrac{6}{7}\)