-What is the result of 1 + 3-5 + 7-9 + 11 -. - 2001 + 2003?

-What is the result of 1 + 3-5 + 7-9 + 11 -. - 2001 + 2003?

This problem is first seen as a series of arithmetic problems with a tolerance of 2 and a first term of one
According to the formula an = a1 + (n-1) d
An = 2003, A1 = 1, d = 2, n is the number of items
There are 1002 items in this sequence
-1 + 3-5 + 7-9 + 11 -. - 2001 + 2003 sequence, observation shows that every two terms add up to be equal to 2
For example (- 1 + 3 = 2, - 5 + 7 = 2.)
If every two numbers are one term, there are 1002 / 2 = 501 items
Then the value is 501 × 2 = 1002
The answer is 1002

Calculate 1 + (- 3) + 5 + (- 7) + 9 + (- 11) +... + 2001 + (- 2003) + 2005

How many odd terms are there from 1 to 2003? An = a1 + (n-1) d, d = 2, an = 2003, A1 = 1, OK, n = 1002, so there are 501 groups. So 501 × (- 2) + 2005 = 1003
The second kind: 1.5.9 ············· - 2003 is the arithmetic difference; 3, - 7, - 11 ······ - 2003 is the arithmetic difference, which can be calculated separately by the summation formula and then added. The number of their terms can also be calculated by one method

Title (1) 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 +... + 2001 + 2003 =? （2）1/1*2+1/2*3+1/3*4+...+1/2008*2009+1/2009*2010=? Note: 1 * 2 in 1 / 1 * 2 is the denominator and the numerator is 1

This is an arithmetic sequence with 1002 items in total
（1+2003）*1002/2=1004004
2 1/n*（n+1）=1/n-1/（n+1）
therefore
1/1*2+1/2*3+1/3*4+...+1/2008*2009+1/2009*2010
=1-1/2+1/2-1/3+1/3-1/4...+1/2008-1/2009+1/2009-1/2010
You can see that the middle items are all gone
=1-1/2010
=2009/2010

Calculate 1 (- 3) + 5 (- 7) + 9 (- 11) +. + 2001 + (- 2003)

-1002

1 × 1 / 3 + 3 × 5 + 5 × 7 + 7 × 9 · 2001 × 2003 =? It's due tomorrow

=1/2(1-1/3)+1/2(1/3-1/5)+…… +1/2(1/2001-1/2003)
=1/2[1+(1/3-1/3)+(1/5-1/5)+…… +(1/2001-1/2001)-1/2003]
=1/2(1-1/2003)
=1/2×2002/2003
=1001/2003

1/1*3+1/3*5+1/5*7+1/7*9.+1/2001*2003

The original formula = (2 / 1 * 3 + 2 / 3 * 5 + 2 / 5 * 7 + 2 / 7 * 9 + +2/2001*2003）/2
=（1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+…… 1/2001-1/2003）/2
=（1-1/2003）/2
=1001/2003

Two thirds of a number is equal to 12. What is 4 / 9 of this number?

12 ÷ 2/3　× 4/9 = 18　× 4/9 = 8

How much less 1 / 4 is 1 / 4 less than 1 / 3 of its reciprocal? 2. 4 / 9 of a number is 36. What is 1 / 9 of this number? 3. 1 / 2 of a number is 10 more than its 1 / 3

1, 13 of 12
2,36 ,4
3,60

9 / 10 of a number is 3 / 4. What is this number?

3/4/(9/10)=5/6

Seven 20% of 8 is equal to 14% of a number 15, what's the number?

Seven
8×20%÷14
Fifteen
=7
8×1
5×15
14，
=3
16；
A: the number is 3
16．