bai 4: tinh bang cach thuan tien nhat: a, 5/9*5/2+4/9*5/2 , b, 12*3/4-3/4*12/7 lam kieu gi
giup minh voi
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bai 4 tinh bang cach thuan tien nhat: b, 12/7*3/4-3/4*12/7 giup minh voi
\(\dfrac{12}{7}\) \(\times\) \(\dfrac{3}{4}\) - \(\dfrac{3}{4}\) \(\times\) \(\dfrac{12}{7}\)
= \(\dfrac{9}{7}\) - \(\dfrac{9}{7}\)
= 0
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Tinh bang cach thuan tien nhat
4/7-2/5+17/7-3/5
giup minh voi minh dang can gap
= 17/7 + 4/7 - 2/5 + 3/5
= 21/7 - 5/5
= 3 - 1
= 2
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BAI 1 : TINH NHANH BANG CACH THUAN TIEN NHAT :
A} 13/4 + 7/12 + 3/4 + 17/12
B} 1 VA 2/3 + 4 VA 4/7 + 5 VA 1/3 + 6 VA 3/7
C} 3/4 * 7/9 = 3/4 * 2/9
D} 3/4 * 4/5 * 5/6
BAI 3 : TINH
A} 3/4 CUA 16 KG .....
B} 7/12 CUA 840 M .....
C} 13/15 CUA 135 M3 .....
D} 6/7 CUA 280 L......
Tinh bang cach thuan tien nhat
3/2 + 4/9 + 4/7 + 5/9
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
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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
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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
tinh bang cach thuan tien nhat : 1+2-3-4+5+6-7-8+9+...+2013+2014-2015-2016
Bai tap:tinh bang cach thuan tien nhat:
a 1/3+2/3+...+10/3+11/3=
b 9+9/2+9/4+9/8+...+9/128+9/256=
c) 5/3+5/3.5+5/5.7+...+5/101.103=
a) = \(\frac{1+2+3+..+11}{3}=\frac{\left(1+11\right)+\left(2+9\right)+..+\left(5+7\right)+6}{3}=\frac{12.5+6}{3}=\frac{66}{3}=22\)
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b) A = \(9+\frac{9}{2}+\frac{9}{4}+\frac{9}{8}+...+\frac{9}{128}+\frac{9}{256}\)
2 x A = 18 + 9 + \(\frac{9}{2}+\frac{9}{4}+\frac{9}{8}+...+\frac{9}{128}\)
Lấy 2 x A - A = 18 - \(\frac{9}{256}\)
A = 4599/256
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c) \(B=\frac{5}{1\times3}+\frac{5}{3\times5}+\frac{5}{5\times7}+...+\frac{5}{101\times103}\)
\(B=\frac{5}{2}\times\left(\frac{2}{1\times3}+\frac{2}{3\times5}+\frac{2}{5\times7}+...+\frac{25}{101\times103}\right)\)
\(B=\frac{5}{2}\times\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+...+\frac{1}{101}-\frac{1}{103}\right)=\frac{5}{2}\times\left(1-\frac{1}{103}\right)\)= 255/103
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giup minh
tinh bang cach thuan tien
7/9 x 5/16 : 5/9 x 4/7
7/9 x 5/16 : 5/9 x4/7
=7/9 x 5/16 x9/5 x 4/7
=7/9 x 45/80 x 4/7
=7/9 x 9/16 x 4/7
=7 x 9 x 4 /9 x 16 x 7
=1/4
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