1.Tính nhanh
\(2+3+4+5+6+7+8=\)
๖ۣۜKết ๖ۣۜBạn vs mk nha
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tính nhanh :
a) ( 3 - 1/4 + 2/3 ) - ( 5 + 1/3 - 6/5 ) - ( 6 - 7/4 + 3/2 )
giúp mk vs nha mai nộp bài r
a) \(\left(3-\frac{1}{4}+\frac{2}{3}\right)-\left(5+\frac{1}{3}-\frac{6}{5}\right)-\left(6-\frac{7}{4}+\frac{3}{2}\right)\)
\(=3-\frac{1}{4}+\frac{2}{3}-5-\frac{1}{3}+\frac{6}{5}-6+\frac{7}{4}-\frac{3}{2}\)
\(=3-\frac{1}{4}+\frac{7}{4}-\frac{3}{2}+\frac{2}{3}-\frac{1}{3}-5+\frac{6}{5}-6\)
\(=3+\frac{3}{2}-\frac{3}{2}+\frac{1}{3}-11+\frac{6}{5}\)
\(=3+0+\frac{23}{15}-11\)
\(=\frac{68}{15}-\frac{165}{15}=\frac{-97}{15}.\)
a) 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10
= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 5 + 10
= 10 + 10 + 10 + 10 + 10 + 5
= 10 x 5 + 5
= 55
b) ( 9 + 1 ) + ( 3 + 7 ) + ( 2 + 8 ) + ( 5 + 5 ) + ( 4 + 6 ) + ( 3 + 7 ) + ( 6 + 4 ) + ( 2 + 99 ) + 100
= 10 +10 + 10 + 10 + 10 + 10 + 10 + 101 + 100
= 10 x 7 + 101 + 100
= 70 + 100 + 101
= 271
Chuc ban hoc tot
a) 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10
= ( 1 + 9 ) + ( 2 + 8 ) + ( 3 + 7 ) + ( 4 + 6 ) + 10 + 5
= 10 + 10 + 10 + 10 + 10 + 5
= 10 * 5 + 5
= 50 + 5
= 55
b) ( 99 + 1 ) + ( 1 + 3 + 7 + 2 + 5 + 9 + 6 + 5 + 4 + 7 + 2 +3 + 8 ) +100
= 100 + 71 + 100
= 171 + 100
= 271
1 + 2 -3-4 + 5 + 6-7-8+...+2017+2018
= 1 + (2-3-4+5) + (6-7-8+9) + ...+ (2014-2015-2016+2017) + 2018
= 1 + 0+0+...+0+2018
=2 019
a, (x + 2) + (x + 4) + (x + 6) + ... + (x + 50) = 750
=> x + 2 + x + 4 + x + 6 + ... + x + 50 = 750
=> (x + x + x + ... + x) + (2 + 4 + 6 + ... + 50) = 750
=> 25x + (50 + 2).25 : 2 = 750
=> 25x + 52.25 : 2 = 750
=> 25x + 650 = 750
=> 25x = 100
=> x = 4
a) ( x+x+...+x)+(2+4+6+...+50)= 750
( x*25)+ (50+2)*25:2 = 750
(x*25)+ 650 = 750
x* 25 = 750 - 650 = 100
x = 100 :25 = 4
28 + 94 + 6 + 372 = ( 94 + 6 ) + ( 28 + 372 )
= 100 + 400
= 500
7/8 + 5/6 = 41/24
4/8 : 3/5 = 5/6
=(2+8)+(3+7)+(4+6)+5
=10+10+10+5
=30+5
=35
2 + 3 + 4 + 5 + 6 + 7 + 8
= (2 + 8) + (3 + 7) + (4 + 6) + 5
= 10 + 10 + 10 + 5
= 10 x 3 + 5
= 30 + 5
= 35