Tính nhanh
a) (-49)--|-145|+(-2017)+|245|+(-51)
b) -99(2-678)-678.99
1) Tính nhanh
a) (-8-12):|-5|
b) (-49)-|-145|+(-2017)+|245|+(-51)
c) 79.|-39|-21.|-39|
d) -99(2-678)-678.99
a,(-8-12):/-5/=-20:5=4(ban oi con nay ko tinh nhanh dc)
b,(-49)-/-145/+(-2017)+/245/+(-51)=(-49+am 51)-145-2017+245=-100+100-2017=0-2017=-2017
c lam theo con gai obama minh ko chac ban tinh lai ket qua xem
d,-99(2-678)-678.99=-99.676+678.(-99)=-99.676+678.(-99)=-99(676+678)=-99.1345=-133155(tinh lai ket qua nha)
c) 79.l-39l -21.l-39l
=79.39 -21.39
=39.(79 -21)
=39.58=3364
a) (- 8 - 12 ) : | - 5 | = - 20 : 5 = - 4
b) ( - 49 ) - | - 145 | + ( - 2017 ) + | 245 | + ( - 51 )
= - 49 - 145 - 2017 + 245 - 51
= ( - 49 - 51 ) + ( - 145 + 245 ) - 2017
= - 100 + 100 - 2017
= 0 - 2017 = - 2017
c) Bạn cho đề rõ ra nhé !!!!
d) - 99 . ( 2 - 678 ) - 678 . 99
= - 99 . ( - 676 ) - 67122
= 66924 - 67122
= - 198
tính hợp lí
(-99).(2-678)-678.99
bài 7:tính nhanh
a (145 x 99+145)-(143 x 102-143) b,54 x 47 - 47 x 53 - 20 -27
c, 10000 - 47 x 72 - 47 x 28 d, 3457 - 27 x 48 - 48 x 73 + 6543
a) \(\left(145\times99+145\right)-\left(143\times102-143\right)\)
\(=\left[145\times\left(99+1\right)\right]-\left[143\times\left(102-1\right)\right]\)
\(=\left(145\times100\right)-\left(143\times101\right)\)
\(=14500-14443\)
\(=57\)
b) \(54\times47-47\times53-20-27\)
\(=47\times\left(54-53\right)-20-27\)
\(=47-20-27\)
\(=0\)
c) \(10000-47\times72-47\times28\)
\(=10000-47\times\left(72+28\right)\)
\(=10000-47\times100\)
\(=10000-4700\)
\(=5300\)
d) \(3457-27\times48-48\times73+6543\)
\(=\left(3457+6543\right)-48\times\left(27+73\right)\)
\(=10000-48\times100\)
\(=10000-4800\)
\(=5200\)
1) Tính nhanh:
a, 125 x 3 + 125 x 125 x 6
b, ( 245 x 99 + 245 ) - ( 145 x 101 - 145 )
c, 154 x ( 28 + 52 ) - 45 x ( 26 + 54 )
a) 125.3+125.125.6
=125.3+125.750
=125.(3+750)
=125.753
=94125
b) (245.99+245)-(145.101-145)
=(245.(99+1))-(145.(101-1))
=245.100-145.100
=(245-145).100
=100.100
=10000
c) 154.(28+52)-45.(26+54)
=154.80-45.80
=(154-45).80
=109.80
=8720
a) 125x3+125+125x6
=125x(3+1+6)
=125x10
=1250
b) (245x99+245)-(145x101-145)
=(245x99+245)-(145x100)
=(245x100)-14500
=24500-14500
10000
c) 154x80-45x80
=80x(145-45)
=80x100
=8000
a, 125 x 3 + 125 x 125 x 6
=125 x 3 + 125 x 750
=125 x( 3+750)
=125 x753
=94125
b, ( 245 x 99 + 245 ) - ( 145 x 101 - 145 )
=[245 x ( 99+1 )] - [145 x ( 101-1 )]
=( 245 x 100 ) - ( 145 x 100 )
=24500 - 14500
=10 000
c, 154 x ( 28 + 52 ) - 45 x ( 26 + 54 )
=154 x 80 - 45 x 80
=(154-45)x80
=109 x80
=8720
Tính nhanh
a/ 2017 x 8 + 2 x 2017
b/3/7 x 9/7 - 2/7 x 3/7
\(a,2017\times\left(8+2\right)=2017\times10=20170\\ b,=\dfrac{3}{7}\times\left(\dfrac{9}{7}-\dfrac{2}{7}\right)=\dfrac{3}{7}\times1=\dfrac{3}{7}\)
Bài 2: Tính nhanh
a) (35-815)-(795-65)
b) 5-197-2015-2015
c) 1259-1409-12+1259+1409
d) -5+(-37)-45+151-37+151
e) 53-145-359-53+145-259
\(a.\left(35-815\right)-\left(795-65\right)\\ =35-815-795+65\\ =\left(35+65\right)-\left(815+795\right)\\ =100-1610=-1510\)
Bài 2:
a: Ta có: \(\left(35-815\right)-\left(795-65\right)\)
\(=35-815-795+65\)
\(=100-1600\)
=-1500
b: Ta có: \(5-197-2015-2015\)
\(=-2010-2212\)
=-4222
c: Ta có: \(1259-1409-12+1259+1409\)
\(=2518-12\)
=2506
Tính B=1*3+5*7+9*11+...+97*101
C=1*3*5-3*5*7+5*7*9-....-97*99*101
D=1*99+3*97+5*95+...+49*51
E=1*3^3+3*5^3+5*7^3+...+49*51^3
F=1*99^2+2*98^2+3*97^2+...+49*51^2
cái này bạn mở sách bồi dưỡng toán ra trang gần cuối là thấy ngay ấy mà
Tính: \(B=\frac{100^2+1^2}{100\cdot1}+\frac{99^2+2^2}{99\cdot2}+\frac{98^2+3^2}{98\cdot3}+...+\frac{52^2+49^2}{52\cdot49}+\frac{51^2+50^2}{51\cdot50}\)
Bài 2: Bỏ ngoặc rồi tính
1/ -2020 + (1543 + 2020)
2/ (245 – 97) – 245
3/ (-145) – (118 – 145)
4/ (-36 + 89) - (145 + 89 – 36)
1/ -2020 + (1543 + 2020)
\(=-2020+1543+2020\)
\(=-2020+2020+1543\)
\(=0+1543\)
\(=1543\)
2/ (245 – 97) – 245
\(=245-97-245\)
\(=245-245-97\)
\(=0-97\)
\(=-97\)
3/ (-145) – (118 – 145)
\(=-145-118+145\)
\(=-145+145-118\)
\(=0-118\)
\(=-118\)
4/ (-36 + 89) - (145 + 89 – 36)
\(=-36+89-145-89+36\)
\(=\left(-36+36\right)+\left(89-89\right)-145\)
\(=0+0-145\)
\(=-145\)
học tốt
1/ -2020+(1543+2020)
=-2020+1543+2020
=(-2020+2020)+1543
=0+1543=1543
2/ (245-97)-245
=245-97-245
=(245-245)-97
=0-97=-97
3/ -145-118+145
=(-145+145)-118
=0-118=-118
4/ -36+89-145-89+36
=(-36+36)+(89-89)-145
=0+0-145=-145