Tinh nhanh:
( 1 x 2 x 3 x 4 x..........x 100) x ( 679 + 679 x 123 - 679 x 124 )
tinh bằng cách thuận nhất
564 x 8 - 64 x 4 x 2
37 x 18 - 9 x 74 + 100
679 x 78 + 679 x 23 - 679
\(a,564\times8-64\times4\times2=564\times8-64\times8=8\times\left(564-64\right)=8\times500=4000\\ b,37\times18-9\times74+100\\ =37\times2\times9-9\times74+100\\ =\left(74\times9-9\times74\right)+100=0+100=100\\ c,679\times78+679\times23-679=679\times\left(78+23-1\right)\\ =679\times100\\ =67900\)
Tính nhanh :
679 +679 x 123 - 679 x 24
245 x 327 - 245 x 18 - 9 x 245
679+679x123-679x24
=679x1+679x123+679x24
=679x(1+123-24)
=679x100
=67900
245x327-245x18-9x245
=245x(327-18-9)
=245x300
=73500
679 +679 x 123 - 679 x 24
= 679 x ( 1 + 123 - 24 )
= 679 x 100
= 67900
245 x 327 - 245 x 18 - 9 x 245
= 245 x ( 327 - 18 - 9 )
= 245 x 300
= 73500
679+679x123-679x24
=679x1+679x123-679x24
=679x(1+123-24)
=679x100
=67900
245x327-245x18-9x245
=245x(327-18-9)
=245x300
=73500
tính bằng cách thuận tiên nhất a 36 x 532 63 x 532 532b 679 679 x 123 679 x 24c 245 x 327 245 x 18 9 x 245
tính bằng cách thuận tiên nhất:
a) 36 x 532 + 63 x 532 + 532
b) 679 + 679 x 123 - 679 x 24
c) 245 x 327 - 245 x 18 - 9 x 245
a) 36 x 532 + 63 x 532 + 532
= 532 x (36 + 63 + 1)
= 532 x 100
= 53200
b) 679 + 679 x 123 - 679 x 24
= 679 x (1 + 123 - 124)
= 679 x 0
= 0
c) 245 x 327 - 245 x 18 - 9 x 245
= 245 x (327 - 18 - 9)
= 245 x 300
= 73500
a)
\(36\times532+63\times532+532\)
\(=36\times532+63\times532+532\times1\)
\(=532\times\left(36+63+1\right)\)
\(=532\times100\)
\(=53200\)
b)
\(679+679\times123-679\times24\)
\(=679\times1+679\times123-679\times24\)
\(=679\times\left(1+123-24\right)\)
\(=679\times100\)
\(=67900\)
c)
\(245\times327-245\times18-9\times245\)
\(=245\times\left(327-18-9\right)\)
\(=245\times300\)
\(=73500\)
a)
36 x 532 + 63 x 532 + 532
= 36 x 532 + 63 x 532 + 532 x 1
= ( 36 + 63 + 1 ) x 532
= 100 x 532
= 53200
b)
679 + 679 x 123 - 679 x 24
= 679 x 1 + 679 x 123 - 679 x 24
= 679 x ( 1 + 123 - 24 )
= 679 x 100
= 67900
c)
245 x 327 - 245 x 18 - 9 x 245
= 245 x ( 327 - 18 - 9 )
= 245 x 300
= 73500
(125 -679 + 145 ) - ( 125 - 679 )
(x - 29 ) - ( 17 - 38 ) = -9
( x + 5 ) + ( x - 9 ) = x + 2
( 27 - x )+ ( 15 + x ) = x - 24
-359 + 181 + ( -123 ) + 350 + ( -172 )
13 - 12 + 11 + 10 - 9 + 8 - 7 -6 + 5 - 4 + 3 + 2 -1
a) (125 -679 + 145 ) - ( 125 - 679 )=125 -679+145-125+679=145
b)(x - 29 ) - ( 17 - 38 ) = -9
<=> x-29 -17+38=-9
<=>x=-1
c)( x + 5 ) + ( x - 9 ) = x + 2
<=>x+5+x-9=x+2
<=>x+x-x=2+9-5
<=>x=6
d) ( 27 - x )+ ( 15 + x ) = x - 24
<=> 27-x+15+x-x=-24
<=> -x=-66
<=>x=66
e) -359 + 181 + ( -123 ) + 350 + ( -172 ) = (181 +350)-(359+172) -123 =531-531-123=-123
f) 13 - 12 + 11 + 10 - 9 + 8 - 7 -6 + 5 - 4 + 3 + 2 -1=( 13 - 12) +11 + (10 - 9)+(8-7)-6+(5-4)+3+(2-1)=1+11+1+1-6+1+3+1=13
a, (125 -679 + 145 ) - ( 125 - 679 )
= 125 - 679 + 145 - 125 + 679
= ( 125 - 125 ) + ( -679 + 679 ) + 145
= 0 + 0 +145
= 145
b, (x - 29 ) - ( 17 - 38 ) = -9
x - 29 - 17 + 38 = -9
x - 29 - 17 = -9 - 38
x - 29 - 17 = -47
x - 29 = -47 + 17
x - 29 = -30
x = -30 + 29
x = -1
Vậy x = -1
c, ( x + 5 ) + ( x - 9 ) = x + 2
x + 5 + x - 9 = x + 2
x - x + 14 = x + 2
14 = x + 2
x = 14 - 2
x = 12
Vậy x = 12
d, ( 27 - x )+ ( 15 + x ) = x - 24
27 - x + 15 + x = x - 24
42 + ( -x + x ) = x - 24
42 = x - 24
x = 24 + 42
x = 66
Vậy x = 66
e, -359 + 181 + ( -123 ) + 350 + ( -172 )
= ( -359 + 350 ) + [ 181 + ( -172 ) ] + ( -123)
= (-9) + 9 + ( -123 )
= 0 + ( -123)
= (-123)
g , 13 - 12 + 11 + 10 - 9 + 8 - 7 -6 + 5 - 4 + 3 + 2 -1
= ( 13 - 12 ) + ( 10 - 9 ) + ( 8 - 7 ) + ( 5 - 4 ) + ( 2 - 1 ) + ( 11 - 6 + 3)
= 1 + 1 + 1 + 1 + 1 + 8
= 1. 5 + 8
= 5 + 8
= 13
A) 36x532+ 63 x 532 + 532 b)679 + 679 x 123 - 679 x 24 c) 245 x 327 - 245 x 18 -9 x 245
a)
36 x 532 + 63 x 532 + 532
= 36 x 532 + 63 x 532 + 532 x 1
= ( 36 + 63 + 1 ) x 532
= ( 99 + 1 ) x 532
= 100 x 532
= 53200
b)
679 + 679 x 123 - 679 x 24
= 679 x 1 + 679 x 123 - 679 x 24
= 679 x ( 1 + 123 - 24 )
= 679 x ( 124 - 24 )
= 679 x 100
= 67900
c)
245 x 327 - 245 x 18 - 9 x 245
= 245 x ( 327 - 18 - 9 )
= 245 x ( 309 - 9 )
= 245 x 300
= 73500
c) 562 x 8 +562 x 95 -562 x 3
d)679 x 99 + 679
8. Bỏ dấu ngoặc rồi tính:
a) ( 17 – 229) + ( 17 - 25 + 229) ; b) ( 125 – 679 + 145) – ( 125 – 679 )
9. Tìm x biết: a) 15 – ( 4 – x) = 6 ; b) - 30 + ( 25 – x) = - 1 ;
c) x – ( 12 – 25) = -8 ; d) ( x – 29 ) – ( 17 – 38 ) = - 9
10. Tìm số nguyên x biết: a) x – 5 = - 1 ; b) x + 30 = - 4; c) x – ( - 24) = 3 ; d) 22 – ( - x ) = 12; e) ( x + 5 ) + ( x – 9 ) = x + 2 ; f) ( 27 – x ) + ( 15 + x ) = x – 24 .
Giá trị của biểu thức: 679 x 85 + 679 x 15 là
679 x 85 + 679 x 15
= 679 x ( 85 + 15 )
= 679 x 100
= 67900