What do you do with 21 30 , 35 70 , 55 100 tasks?!

60 problem-solving questions for 5th grade.

50 for even, 50 for odd.

50 even numbers:

50 odd numbers:

In natural numbers 1 to 100, there are 50 even numbers and 50 odd numbers.

All integers are either odd (singular) or even (even). If a number is a multiple of 2, it is an even number (double) and can be expressed as 2n; If not, it is an odd number (singular), which can be expressed as 2n+1 (n is an integer), i.e. the remainder of the odd number (singular) divided by two is one.

Odd number (English: odd), also known as singular number, in the integer, the number divisible by 2 is even, the number not divisible by 2 is odd, and the single digit of the odd number is 1, 3, 5, 7, 9. Even numbers can be represented by 2k, odd numbers can be represented by 2k+1, where k is an integer.

Number series: 1, 3, 5, 7, 9 ,......2n-1，..It is called an odd number sequence, and the general formula is.

It has a graceful property: when n takes any positive integer, its first n terms are all perfectly squared, i.e. .

The odd sequence can also be expressed from another angle: if, when.

time, there are. then the series.

is an odd-numbered sequence. Extended Materials

Regarding odd and even numbers, there are the following properties:

1) There must be an odd number and an even number in two consecutive integers;

2) Odd + Odd = Even; Even + Odd = Odd; Even + Even + ...Even + Even + ...

3) Odd - Odd = Even; Even + Odd = Odd; Odd - Even = Odd;

4) If a and b are integers, then a+b and a-b have the same parity, that is, a+b and a-b are both odd or even;

5) The product of n odd numbers is odd, and the product of n even numbers is even; If one of the equations is an even number, then the product is an even number;

6) The odd number of single digits is ; The single digits of the even number are ;

7) the square of the odd number divided by the remainder 1;

8) The square difference of any two odd numbers is a multiple of .

9) Odd numbers divided by 2 and the remainder is 1

Within 1 to 100 natural numbers, there are (50) even numbers and (50) odd numbers.

50 odd numbers:

50 even numbers:

1 100 of 100 counts.

1 3 5 7 ..99 is an odd number, a total of 50.

2 4 6 8 ..100 is an even number, a total of 50.

Within the natural numbers 1 to 100, there are several even numbers, 50 even numbers, and 50 odd numbers. Inside.

50 even numbers: capacity.

50 odd numbers:

There are 50 even numbers and 50 odd numbers in 100.

50 odd and 50 even, where o is not.

There are 25 prime numbers from 1 to 100 and 50 even numbers.

In natural numbers 1 to 100, there are 50 even numbers and 50 odd numbers.

50 even numbers:

50 odd numbers:

All integers are either odd (singular) or even (even). If a number is a multiple of 2, it is an even number (double) and can be expressed as 2n; If not, it is an odd number (singular), which can be expressed as 2n+1 (n is an integer), i.e. the remainder of the odd number (singular) divided by two is one.

How to quickly calculate addition and subtraction within 20? It's just too simple to calculate with the broken ten method, and it's super practical.

The first step in learning a fast algorithm is to know your hands.

In order to attract the attention of the toddler, first let the child play finger games, the hand and the palm surface, straighten the fingers, and the toddler can observe the thumb alone.

The second reminds the child that the left hand represents 10, the right hand represents the number, the thumb each represents 5, and the other 4 fingers represent 1, according to the thumb respectively, the index finger, middle finger, ring finger, little finger, the number is 67, 89, so 5 fingers can represent the number 9.

When the right hand is nine, the fist is 0, and the left index finger represents 10, it is decimal.

In this way, each number from 0 to 99 is repeated, and the movements of the feet can represent hundreds within 300.

It should be emphasized repeatedly in teaching"The left hand is 10, and the right hand is a little"。

Use your finger to locate the formula to help your child identify.

The first step in learning the finger fast algorithm is to know your hands. In order to attract the attention of the toddler, let the toddler play finger games first, with the palms of both hands facing inward, and the five fingers straightened, and the toddler can observe the thumbs facing up alone. Next, remind the child that the left hand represents ten, the right hand represents the unit, the thumb represents 5, the other 4 fingers each represent 1, and then the index finger, middle finger, ring finger, and little finger are respectively on the basis of the thumb, and the numbers represented are , so that 5 fingers can represent the number 9.

When the right hand is full of nine, the five-finger fist represents 0, and the index finger of the left hand represents 10, which is the decimal system. This repeated cycle represents each digit from 0 to 99, supplemented by the movement of both feet, which can represent hundreds of digits up to 300. When teaching young children, it is necessary to repeatedly emphasize that "the left hand is the ten, and the right hand is the unit".

And with the help of finger positioning formulas to help children distinguish.

The mantra of abdication and subtraction within 10.

1 refund, 1 return, 9 2 refund, 1 return, 8 3 return, 1 return, 7 4 return, 1 return, 6 return, 6 return, 1 return, 4

7 back 1 return 3 8 back 1 return 2 9 back 1 return 1 return 1

The formula for abdication and subtraction within 10 is:

For example: 10-7 (first out of 1 in the 10th place, and then use the abdication of 7 to subtract the formula to return 1 to 3 in the single place) = 3

The above exercises are the practice methods of addition and subtraction within 10 years of kindergarten children, children are very fond of this method, and they are playing and operating while counting in the finger game, which is helpful for the development of children's intelligence. And the calculation accuracy is high, especially suitable for kindergarten children to learn, if you want to calculate the exercises within 20 to 100, you can also continue to explore and summarize on this basis.

Note: Right index finger 1,6. Right thumb 5. Left index finger 10,60. Left thumb 50.

Subtraction within 20 sometimes requires abdication, such as 13-5, 1 on the left hand, 3 on the right hand (index finger, middle finger, ring finger), 1 back on the left hand, and thumb extension (+5) on the right hand, i.e. 8 (index finger, middle finger, ring finger, thumb extension of the right hand).

Each finger is not finger horizontal, one finger is 3 numbers, ten fingers are a total of 28 numbers, you can subtract the number within 20.

Then ask the students to talk about the calculation method, which number to divide first, and how to divide it? What happens after the points are divided? When talking about the calculation process, towards.

The teaching content of this unit is abdication subtraction within 20, one is the subtraction of more than a dozen subtractions that need to abdicate, referred to as abdication and subtraction within 20.

This doom ......This is the Fibonacci sequence, specifically 2+3=5, 3+5=8, 5+8=13, and so on.

So the original = 2+3+(2+3)......

But it's complicated, so use formulas.

The nth number an=(1 5)*

The formula is also complicated, but correct, so a slightly easier way is to use this formula to find 100, 97, 94 ...... respectivelyThe fourth number, then add up the numbers *2 and add 2 to get the result.

The estimation result is relatively large, so there should be an easier way ==

Fibonacci sequence.

It's a bit cumbersome to derive.

Refer to the encyclopedia.

There is a derivation process.

Very scary answer 2427893228399980000000

Programmed to get it absolutely right.

Answer: Because the number that satisfies the single digit is 0 or 5 is divisible by 5, that number is a multiple of 5. So it's a multiple of 5.

is a multiple of five. Characteristics of multiples of five: The number in the single digit is 5 or 0.