tinh bang 2 cach
[16432+82528]:4
120:[8*5]
[18*24]:6
tinh bang 2 cach
a, ( 25 + 45 ) : 5
b, 24 : 6 + 36 : 6
a (25 + 45) : 5 = 70 : 5 = 14
(45 + 25) : 5 = 45 : 5 + 25 : 5 = 9 + 5 = 14
b 24 : 6 + 36 : 6 = 4 + 6 = 10
24 : 6 + 36 : 6 = (24 + 36) : 6 = 60 : 6 = 10
`a)`
`@C1:`
`(25+45):5=70:5=14`
`@C2:`
`(25+45):5=25:5+45:5=5+9=14`
`b)`
`@C1:`
`24:6+36:6=(21+36):6=60:6=10`
`24:6+36:6=4+6=10`
C1:a,(25 + 45) : 5
= 70 : 5
= 14
C2:
(45 + 25) : 5
= 45 : 5 + 25 : 5
= 9 + 5
= 14
C1b, 24 : 6 + 36 : 6
= 4 + 6
= 10
C2:
24 : 6 + 36 : 6
= (24 + 36) : 6
= 60 : 6
= 10
1+2+3+4++5+6+7+8+9+10+11+12+13+14++15+16+17+18+19+20
Hoi tong tren bang bao nhieu (tinh nhanh va giai thich cach lam)
Ta có: 1+2+3+…+20=20.(20+1):2=20.21:2=420:2=210
khoảng cách: 2-1=1
số số hạng là: (20-1):1+1=20(số)
tổng là: (20+1)x20:2=210
1+2+3+4+5+6+7+8+9
tinh bang cach thuan tien nhat
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9
= (1 + 9) + (2 + 8) + (3 + 7) + (4 + 6) +5
= 10 + 10 + 10 +10 + 5
= 10 x 4 + 5
= 40 + 5
= 45
1+2+3+4+5+6+7+8+9
=[1+9]+[2+8]+[3+7]+[4+6]+5
=10+10+10+10+5
=40+5
=45
tinh bang cach thuan tien nhat : 1+2-3-4+5+6-7-8+9+...+2013+2014-2015-2016
Tinh bang hai cach
5/24×5/12×24
tinh bang cach thuan tien nhat : 3/4 x 4/5 + 5/6 x 6/7 x 7/8
Tinh Bang Hai Cach
(6/7-4/7):2/5 = ?
8/15 : 2/11 + 7/15 : 2/11=?
Tinh bang cach thuận tien 4+8+12+16+20+24+28????
4+8+12+16+20+24+28
= (16+24)+(28+12)+20+4+8
= 40+40+20+12
= 112
tinh bang cach thuan tien nhat
1+2+3+4+5+6+7+8+9:9 =
1+2+3+4+5+6+7+8+9:9
=1+2+3+4+5+6+7+8+1
=(1+1)+(2+8)+(3+7)+(4+6)+5
=2+10+10+10+5
=(2+5)+(10+10+10)
=7+30
=37
1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 : 9
= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5 : 9
= 10 + 10 + 10 + 10 + 5 : 9
= 20 + 20 + 5 : 9
= 40 + 5 : 9
= 45 : 9
= 5