Bài 1 : tính nhanh
19 + 199 + 1999
298 + 2998 + 29998 + 299998
25 x 16 x 125
Bài 2 : Tìm x
( x – 11 ) x 7 = 757
x + x + x + 15 = 141
x + x + x + x = 16
54 : ( 1665 – x ) = 1730 – 1724
( 4160 – x ) x 6 = 810 : 3
( x + 426 ) x 2 = 1897 – 989
x : ( 1443 – 1436 ) = 2041 – 1736
Đáp án+Giải thích các bước giải:
Bài 1 :
a) $ 19 + 199 + 1999 $
$ = (199 + 1) + (1999 + 1) + 17 $
$ = 200 + 2000 + 17 $
$ = 2217 $
b) $ 298 + 2998 + 29998 + 299998 $
$ = (299998 + 2) + (29998 + 2) + (2998 + 2) + 292 $
$ = 300000 + 30000 + 3000 + 292 $
$ = 333292 $
c) $ 25$ x $16$ x $125$
$ = (25$ x $4)$ x $125$ x $4$
$ = 100$ x $500$
$ = 50000$
Bài 2 :
a) $( x – 11 )$ x $7 = 757$
$ x – 11 = 757 : 7$
$ x – 11 = 108, 1428571$
$ x = 108, 1428571 + 11$
$ x = 119,1428571$
b) $x + x + x + 15 = 141$
$3*x + 15 = 141$
$3*x = 141 – 15$
$3*x = 126$
$x = 126 : 3$
$x = 42$
c) $x + x + x + x = 16$
$4*x = 16$
$x = 16 : 4$
$x = 4$
d) $54 : ( 1665 – x ) = 1730 – 1724$
$54 : ( 1665 – x ) = 6$
$1665 – x = 54 : 6$
$1665 – x = 9$
$x = 1665 – 9$
$x = 1656$
e) $( 4160 – x ) * 6 = 810 : 3$
$( 4160 – x ) * 6 = 270$
$ 4160 – x = 270 : 6$
$ 4160 – x = 45$
$ x = 4160 – 45$
$ x = 4115$
f) $ ( x + 426 ) * 2 = 1897 – 989$
$ ( x + 426 ) * 2 = 908$
$ x + 426 = 908 : 2$
$ x + 426 = 454$
$ x = 454 – 426$
$ x =28$
g) $ x : ( 1443 – 1436 ) = 2041 – 1736$
$ x : ( 1443 – 1436 ) = 305$
$ x : 7 = 305$
$ x = 305 * 7$
$ x = 2135$
Học tốt!
Bài 1
19+199+1999=(19+1999)+199
=2018+199
=2217
298+2998+29998+299998
=(298-6)+(2998+2)+(29998+2)+(299998+2)
=292+(3000+30000+300000)
=292+333000
=333292
25 x 16 x 125=(25*16)*125=400*125=50.000
Bài 2
(x−11)(x−11) x 7=757
x−11=757:7
x−11=108,1428571
x=108,1428571+11
x=119,1428571
x + x + x + 15 = 141
3x = 141-15
3x =126
3x = 126:3
3x = 42
x + x + x + x = 16
4x = 16
4x = 16 : 4
x = 4
54 : ( 1665 – x ) = 1730 – 1724
54 : ( 1665 – x ) = 6
1665 – x = 54 : 6
1665 – x = 9
x = 1665-9
x =1656
( 4160 – x ) x 6 = 810 : 3
( 4160 – x ) x 6 = 270
4160 – x = 270 : 6
4160 – x = 45
x = 4160-45
x = 4115
( x + 426 ) x 2 = 1897 – 989
( x + 426 ) x 2 = 908
x + 426 = 908 : 2
x + 426 = 454
x + = 454 – 426
x + = 28
x:(1443−1436)=2041−1736
x:(1443−1436)=2041−1736
x:(1443−1436)=305
x:(1443−1436)=305
x: 7 =305
x =305∗7
x = 2135
Sai thì thui nha !