How many odd numbers are there from 1 to 2021?

It can be inferred to solve, and there are five odd numbers from 1 to 10 13579. Then there are 50 odd numbers from 1 to 100, 500 odd numbers from 1 to 1 thousand, 1 to 2 thousand will have 1000 odd numbers, and by calculating how many odd numbers there are in 21, we get 11, so the total number is 1011 odd numbers.

The addition and subtraction of odd and even numbers has the following properties: (1) odd numbers plus odd numbers are even numbers (2) odd numbers plus even numbers are odd numbers can be derived from the above two numbers: (1) odd numbers and odd numbers are odd numbers (2) the sum of multiple even numbers is even numbers 1 to 2021 There are a total of 2021 sum numbers, of which there are 1010 even numbers and 1011 and odd numbers.

Addition and subtraction are operators with the same priority, and the order does not affect the final result, so adding 1 to 2021 is the sum of 1010 and even numbers plus the sum of 1011 odd numbers. 1010 even numbers are even, and the sum of 1011 and odd numbers is odd. So the sum of 1 added to 2021 is an odd number.

1 to 2021 has a total of 2021 numbers, except for 2021 itself, the first 2020 numbers are all odd and even, and there is exactly half of them, that is, 2020 2 = 1010 odd numbers; Add 2021 itself, that is, 1010 + 1 = 1011 odd numbers.

Because there are a total of 2021 numbers from 1 to 2021, half of the odd and even numbers, that is, there are 2020 2+1=1011 odd numbers.

2022 2=1011.

From 1 to 2022, odd and even numbers account for half each, so including 1, the odd number is 2022 2=1011.

Use 2021 2 to round 1011 odd numbers.

1+2021) 2 = 1011 odd numbers.

For example: How many odd numbers are there from 1 to 7?

2021 numbers, 1000 + 10, because the odd number ends, add 1 more, and you get 1011 odd numbers.

2020 2=1010.

There are 1010 odd numbers.

1-2021, 1 included? Should include 1

1010 + 1 = 1011 pcs.

There are 1011 odd numbers.

2023-1=2022 2022 2=1011 1011+1=1012 Answer: There are 1012 odd numbers in 2023.

Solution: The last ten first terms = the sum of 2 terms.

Last ten first items = 2020 2 10

Last term = (number of items - 1) Tolerance + first term.

First term = last term - (number of terms - 1) tolerance.

First term = 404 - first term - (10 1) 2

First term = (404 18) 2

A: The smallest odd number is 193

Let the smallest odd number be x, then the second to tenth odd numbers are x 2....x＋20x＋（x＋2）＋…x＋18）＝2020

10x＋90＝2020

10x＝1930

x＝193

It's so red, it's in a trance, hehehahaha.

Let the smallest odd number be x, then there is:

x+（x+2）+（x+4）+（x+6）+…x+18)=2020, that is, 10x+90=2020

x+9=202

The solution is x=193

So the smallest odd number of them is 193

The sum of 10 consecutive odd numbers is 2020, where the smallest odd number is 193, because the middle even number of 10 consecutive odd numbers is 202, and pushing down 5 odd numbers is 193.

10 consecutive odd numbers, the first known is 10 numbers, and the second difference between the largest and smallest numbers is 18, then.

x+x+18）×10÷2=2020

2x+18）×10=2020×2

20x+180=4040

20x=4040-180

x=3860÷20

193, that is, the minimum number is 193, and the maximum number is 193 + 18 = 211. Can be verified.

x，x+2，……x+18

10 numbers are added together.

10x+90＝2020

10x＝1930

x 193, so the smallest odd number is 193

The first thing to determine is how many odd numbers there are from 1 to 2021, 2021 2=1011According to the law +1011=2022, every two odd numbers are equal to 2022, and among 1011 odd numbers, you can combine 1011 2=505 ......1, the remaining 1 is 1011, so regret, calculate 2022 505 = 1021110 plus 1011, the final result is 1022121.