A. 47
B. 48
C. 49
D. 50
Những câu hỏi liên quan
Hãy tính \(\dfrac{C}{D}\). Biết C= \(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{48}+\dfrac{1}{49}+\dfrac{1}{50}\) và D= \(\dfrac{1}{49}+\dfrac{2}{48}+\dfrac{3}{47}+...+\dfrac{48}{2}+\dfrac{49}{1}\)
=> D + 49 = (1/49 + 1) + (2/48 + 1) +... (49/1 + 1)
= 50/1 + 50/2 + ... + 50/49
= 50(1/2+1/3+...+1/49) + 50
=> D = 50(1/2 + 1/3 +... + 1/49) + 1
= 50(1/2 + 1/3 +... + 1/49 + 1/50)
=> C/D = 1/50
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Tinh ti so a/b
A= 1/2+1/3+1/4+.....+1/48+1/49+1/50
B= 1/49+2/48+3/47+.....+48/2+49/1
cho A = 1/2 + 1/3 + 1/4 + ... +1/50
CHO C = 49/1 + 48/2 + 47/3 +...+ 2/48 + 1/49 = 50.A
chứng tỏ C không phải là số tự nhien
=> \(A=\frac{\left(\frac{49}{1}+\frac{48}{2}+...+\frac{1}{49}\right)}{50}=\frac{49}{50.1}+\frac{48}{50.2}+...+\frac{1}{50.49}\)
=> \(A=\frac{50-1}{50.1}+\frac{50-2}{50.2}+...+\frac{50-49}{50.49}\)
=> \(A=\left(\frac{50}{50.1}+\frac{50}{50.2}+...+\frac{50}{50.49}\right)-\left(\frac{1}{50.1}+\frac{2}{50.2}+...+\frac{49}{50.49}\right)\)
=> \(A=\left(1+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{49}\right)-\left(\frac{1}{50}+\frac{1}{50}+...+\frac{1}{50}\right)\) ( có 49 số 1/50 )
=> \(A=1+\frac{1}{2}+...+\frac{1}{49}-\frac{49}{50}=\left(1-\frac{49}{50}\right)+\frac{1}{2}+\frac{1}{3}+...+\frac{1}{49}\)
=> \(A=\frac{1}{2}+\frac{1}{3}+...+\frac{1}{50}\)
Vậy A không phải là số tự nhiên
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a, B= 263^2 + 74.263 + 37^2
b , C = 136^2 - 92.136;+ 46^2
c , D = ( 50^2 + 48^2 + 46^2 +....+ 2^2 ) - ( 49^2 + 47^2 + 45^2 + ...... + 1^2 )
cho p=1/2+1/3+1/4+…+1/47+1/48+1/49+1/50
q=1/49+2/48+3/49+…47/3+48/2+49/1
tính p/q
Cho \(A=\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{50};B=\dfrac{1}{49}+\dfrac{2}{48}+\dfrac{3}{47}+...+\dfrac{48}{2}+\dfrac{49}{1}\)
Tính giá trị của \(\dfrac{A}{B}\)
\(B=\dfrac{1}{49}+\dfrac{2}{48}+\dfrac{3}{47}+...+\dfrac{48}{2}+\dfrac{49}{1}\)
\(B=\left(\dfrac{1}{49}+1\right)+\left(\dfrac{2}{48}+1\right)+\left(\dfrac{3}{47}+1\right)+...+\left(\dfrac{48}{2}+1\right)+\dfrac{49}{1}\)
\(B=\left(\dfrac{50}{49}+\dfrac{50}{49}+\dfrac{50}{48}+\dfrac{50}{47}+...+\dfrac{50}{2}\right)+1\)
\(B=\dfrac{50}{50}+\dfrac{50}{49}+\dfrac{50}{49}+\dfrac{50}{48}+\dfrac{50}{47}+...+\dfrac{50}{2}\)
\(B=50\left(\dfrac{1}{50}+\dfrac{1}{49}+\dfrac{1}{48}+...+\dfrac{1}{2}\right)\)
\(\Rightarrow\dfrac{A}{B}=\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{49}+\dfrac{1}{50}}{50\left(\dfrac{1}{50}+\dfrac{1}{49}+\dfrac{1}{48}+...+\dfrac{1}{2}\right)}=\dfrac{1}{50}\)
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Bài 1 tính nhẩm
a,199+56
b,1213-997
c,25.28
d,600:25
e,50-49+48-47+46-45+...+4-3+2-1
1a) 199 + 56 = 255
b) 1213 - 997 = 216
c) 25 x 28 = 700
d) 600 : 25 = 24
Ý e mình xin trình bày bài giải:
Số số hạng là:
( 50 - 1 ) : 1 + 1 = 50 ( số )
Có số cặp là:
50 : 2 = 25 ( cặp )
Mỗi cặp có giá trị:
50 - 49 = 1
=> Tổng là:
1 x 25 = 25
Đáp số: 25
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a,199+56=255
b,1213-997=216
c,25.28=700
d,600:25=24
e 50-49+48-47+46-45+......+4-3+2-1=25
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Xem thêm câu trả lời
28 tháng 6 2021 lúc 14:09
Dãy tăng dần các số tự nhiên U gồm : 7 ; 11 ; 15 ; ... ; 195
Số phần tử của dãy U là :
A. 48
B. 49
C. 47
D. 50
Dãy tăng dần các số tự nhiên U gồm : 7 ; 11 ; 15 ; ... ; 195
Số phần tử của dãy U là :
A. 48
B. 49
C. 47
D. 50
Dãy tăng dần các số tự nhiên U gồm : 7 ; 11 ; 15 ; ... ; 195
Số phần tử của dãy U là :
A. 48
B. 49
C. 47
D. 50
Đáp án
A.48
hok tốt nha Sa
Xem thêm câu trả lời
chứng tỏ rằng : 49+48/2+47/3+...+2/48+1/49=50.(1/2+1/3+...+1/50)
Football is perhaps _______ (46) popular game in the world. A football match often _________ (47) about ninety minutes. There are two teams play against each other. Each team has elevenmembers. The players kick the ball ___________ (48) goals. There is a goalkeeper to keep the goal safe. The goal-keeper is allowed to touch the ball _________ (49) hand, while others are not. The team, which scores more goals, is declared the winner. The referee is there to make sure that thegame is fair. It’s ___...
Đọc tiếp
Football is perhaps _______ (46) popular game in the world. A football match often _________ (47) about ninety minutes. There are two teams play against each other. Each team has elevenmembers. The players kick the ball ___________ (48) goals. There is a goalkeeper to keep the goal safe. The goal-keeper is allowed to touch the ball _________ (49) hand, while others are not. The team, which scores more goals, is declared the winner. The referee is there to make sure that thegame is fair. It’s _________ (50) to watch a football match.
46.A. the most B. most C. more D. the more
47.A. last B. lasts C. lasted D. will last
48.A. scoring B. to score C. to score D. score
49.A. by B. in C. to D. for
50.A. interesting B. clumsy C. musical D. exhausted
Football is perhaps _______ (46) popular game in the world. A football match often _________ (47) about ninety minutes. There are two teams play against each other. Each team has elevenmembers. The players kick the ball ___________ (48) goals. There is a goalkeeper to keep the goal safe. The goal-keeper is allowed to touch the ball _________ (49) hand, while others are not. The team, which scores more goals, is declared the winner. The referee is there to make sure that thegame is fair. It’s _________ (50) to watch a football match.
46.A. the most B. most C. more D. the more
47.A. last B. lasts C. lasted D. will last
48.A. scoring B. to score C. to score D. score ( bạn xem lại đề )
49.A. by B. in C. to D. for
50.A. interesting B. clumsy C. musical D. exhausted
(46) A. the most
(47) B. lasts
(48) to score
(49) A. by
(50) A. interesting
Mình làm đầu tiên nên nhớ k đúng cho mình với nha!
Answer :
(46) A
(47) B
(48) B
(49) A
(50) A