tính nhanh S = 1+1/1+2 + 1/1+2+3+4+...+1/1+2+3+4+5+6+8
Tính các tổng sau:
1, S=1-2+3_4+..+25-26
2, S=1-3+5-7+...+49-51
3, S=-1+3-5+7-...-53+55
4, S=2-4+6-8+...+22-24
5, S=-2+4-6+8-...-26+28
6, S=2-5+8-11+...-29+32
7, S=-1+5-9-13-...-41-45
8, S=1-5+9-13+...++89-93
9, S=2-4+6-8+...+202-204
10, S=1-6=11-16+21-26+...+171-176
huhu giúp mình với ạ 2h chiều nay mình phải nộp r =(((
Tính các tổng sau:
1, S=1-2+3_4+..+25-26
S =-1+3-5+7-...-53+55 ( có 28 số hạng )
= (-1+3)+(-5+7)+...+(-53+55) ( có 28:2=14 nhóm )
= 2+2+...+2
= 2 . 14
= 28
3
S =-1+3-5+7-...-53+55 ( có 28 số hạng )
= (-1+3)+(-5+7)+...+(-53+55) ( có 28:2=14 nhóm )
= 2+2+...+2
= 2 . 14
= 28
Tính nhanh :
1/2 + 2/4 + 3/6 + 4/8 + 5/10 + 6/12 =
1/3 + 1/4 + 1/5 + 8/10 + 20/15 + 20/30 =
`1/2+2/4+3/6+4/8+5/10+6/12`
`=1/2+1/2+1/2+1/2+1/2+1/2`
`=1/2*6=3`
`1/3+1/4+1/5+8/10+20/15+20/30`
`=(1/3+1/4)+(1/5+4/5)+(4/3+2/3)`
`=7/12+1+2`
`=7/12+3=43/12`
\(\dfrac{1}{2}+\dfrac{2}{4}+\dfrac{3}{6}+\dfrac{4}{8}+\dfrac{5}{10}+\dfrac{6}{12}\)
\(=\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}+\dfrac{1}{2}\)
\(=\dfrac{1}{2}\times6=3\)
\(------\)
\(\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{8}{10}+\dfrac{20}{15}+\dfrac{20}{30}\)
\(=\dfrac{1}{3}+\dfrac{1}{4}+\dfrac{1}{5}+\dfrac{4}{5}+\dfrac{4}{3}+\dfrac{2}{3}\)
\(=\left(\dfrac{1}{3}+\dfrac{4}{3}+\dfrac{2}{3}\right)+\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\dfrac{1}{4}\)
\(=\dfrac{7}{3}+1+\dfrac{1}{4}\)
\(=\dfrac{28}{12}+\dfrac{12}{12}+\dfrac{3}{12}\)
\(=\dfrac{43}{12}\)
`=1/2+1/2+1/2+1/2+1/2+1/2= 1/2 \times 6=3`
`----`
`=1/3+1/4+1/5+4/5+4/3+2/3 =(4/3+2/3+)+(1/5+4/5)+1/3+1/4=2+1+1/3+1/4=3+1/3+1/4=43/12`
Tính nhanh:
S = 1 - 2 + 3 - 4 + 5 - 6 + ... + 199 - 200
S = 1 + 2 - 3 - 4 + 5 + 6 - 7 - 8 + ... + 97 + 98 - 99 - 100 + 101
Ai giải nhanh nhất mk hứa sẽ tick cho!
S=(1-2)+(3-4)+(5-6)+...+(199-200)
S=(-1)+(-1)+...+(-1)
S=(-1).100=-100
S=1+(2-3)+(-4+5)+...+(98-99)+(-100+101)
S=1+(-1)+1+..+(-1)+1
S=1+25.(-1)+25.1
S=1+(-25)+25
S=1+0
=1
S= 1+(1-3)+3+(1-5)+5+(1-7)+........+199+(1-199)=200
Tính nhanh bằng cách rút gọn rồi tính:
a.(1/2+1/3+1/4+1/5+1/6+1/7+1/8+1/9)-(1/3+1/4+1/5+1/6+1/7+1/8+1/9+1/10)
b.(1/2-1/3)+(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)
Ai nhanh mình tick cho!
a) 1/2
b) 3/8
~~~~~~~~~hok tốt~~~~~~~~~~~~
A/ \(\frac{1}{2}\)
B/ \(\frac{3}{8}\)
Tính nhanh:
a)2+4+8+6+7+8+3+9+2+1;
b)3+2+4+9+7+1+8+6+3+5;
c)2+3+4+5+6+7+8+9+1+4.
a)2+4+8+6+7+8+3+9+2+1;
=(9+1)+(2+8)+(4+6)+(7+3)+(2+8)
=10+10+10+10+10
=10x5
=50
b)3+2+4+9+7+1+8+6+3+5
làm tương tự nhé
c)2+3+4+5+6+7+8+9+1+4.
làm tương tự nhé
P/s tham khảo nha
a) Bạn gộp các số có tổng bằng 10 :2-8,4-6,7-3,8-2,9-1 kq50
b)c) tương tự
\
a)2+4+8+6+7+8+3+9+2+1
=(2+8)+(4+6)+(7+3)+(8+2)+(9+1)
=10+10+10+10+10
=50
b)3+2+4+9+7+1+8+6+3+5
=(3+7)+(2+8)+(4+6)+(9+1)+(3+5)
=10+10+10+10+8
=48
c)2+3+4+5+6+7+8+9+1+4
=(2+8)+(3+7)+(4+6)+(9+1)+(5+4)
=10+10+10+10+9
=49
tính
2/5+1/4 1/3+3/5 1/2+1/4 1/8+5/6
ai lm nhanh e tick cho
\(\dfrac{2}{5}+\dfrac{1}{4}=\dfrac{8}{20}+\dfrac{5}{20}=\dfrac{13}{20}\)
\(\dfrac{1}{3}+\dfrac{3}{5}=\dfrac{5}{15}+\dfrac{9}{15}=\dfrac{14}{15}\)
\(\dfrac{1}{2}+\dfrac{1}{4}=\dfrac{2}{4}+\dfrac{1}{4}=\dfrac{3}{4}\)
\(\dfrac{1}{8}+\dfrac{5}{6}=\dfrac{3}{24}+\dfrac{20}{24}=\dfrac{23}{24}\)
tính nhanh
a,(-3/4 + 5/13):2/7-(2/1/2+8/13):2/7
b,-3/5:(-1/15-1/6)+3/5:(-1/3-1/1/15)
c,(3-1/4+2/3)-(5-1/3-6/5)-(6-7/4+3/2)
A) (-3/4 + 5/13):2/7-(2/1/2+8/13):2/7
\(=\)
\(=\)
B) -3/5:(-1/15-1/6)+3/5:(-1/3-1/1/15)
\(=\)
\(=\)
Tính nhanh
10+2+4+6+8+20
1/3 + 1/6 + 4/3 + 2/6 + 2/3 + 5/6
(10+20)+(2+8)+(4+6)=30+10+10
=50
1/3+1/6+4/3+2/6+2/3+5/6
=(1/3+4/3+2/3)+(1/6+2/6+5/6)
=7/3+8/6=7/3+4/3=11/3
Tính nhanh
1/1 x 2 + 1/ 2 x 3 + 1/ 3 x 4 + 1/ 4 x 5 + 1/ 5 x 6 + 1/ 6 x 7 + 1/ 7 x 8.
\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{6}-\dfrac{1}{7}+\dfrac{1}{7}-\dfrac{1}{8}\)
\(=1-\dfrac{1}{8}=\dfrac{7}{8}\)