The first unit hours, minutes, seconds
For a very short time, the unit with a smaller score is seconds.
Time unit: 1 hour=60 minutes 1 minute=60 seconds 1 hour=3600 seconds
Start time + time=end time
End time - start time=time
End time - time=start time
1. There are (12) large cells on the clock face, and each large cell is divided into (5) small cells. There are a total of (60) small cells on the clock face.
2, the hour hand to go 1 big grid is (1 hour), the minute hand just goes (one circle), is (60 points).
One round of the hour hand is (12 o'clock), and two rounds are (24 o'clock), which is exactly (one day).
3, the minute hand to go 1 small grid is (1 point), the minute hand to go 1 big grid is (5 points).
One minute of the minute hand is (60 points), which is also (1 hour).
4, the second hand to go 1 small grid is (1 second), the second hand to go 1 big grid is (5 seconds).
The second hand is a circle (60 seconds), also (1 minute).
Addition and subtraction within the second and fourth units
The rule of multi-digit addition rule:
1. The same digits should be aligned;
2, from the individual position;
3. Which one is added to the top ten, then advance one by one.
The rule of multi-digit subtraction rule:
1. The same digits should be aligned;
2. Decrease from the position;
3, which one is not enough to reduce, the former one to retreat, add 10 to the standard.
Checking method of addition: addend + addend=and
(1) and - addend=another addendxx
检查减法方法的方法：减法 - 减法=差
1 km=1000 m 1 m=10分米1分米=10 cm 1 cm=-10 mm
The mass of a coin is about 1 gram.
Unit 5 Double understanding
Small × multiple=large ÷ small=multiple ÷ multiple=small
Unit 6 Multi-digit multiplied by a single digit
Any number of 0 is equal to 0.
Multi-digit multiplier rule:
1. From a single digit, multiply each digit of the multi-digit number by a single digit.
2, which one of the superior is full of dozens, then go forward a few.
Simple multiplication: multiplication by multiplier and multiplication at the end of the multiplier, you can multiply the front of 0, zero does not participate in the operation, and several zeros are dropped and added at the end of the product.
Unit 7 Quadrilateral
(1) Features of the quadrilateral:Straight side.
2. There are four corners.
(2) Characteristics of the rectangle:Straight side.
2. The four corners are right angles.
3. The opposite sides are equal.
(3) Characteristics of the square:Straight side.
2. The four corners are right angles.The sides are equal.
(4) Characteristics of parallelograms:Straight sides, opposite sides are equal and parallel.
2, there are four corners, the diagonal is equal.
3, easy to deform.
Perimeter: The length of a closed figure for a week is its perimeter.
The circumference of the rectangle=(length + width) × 2 The letter indicates: C=(a + b) × 2
Rectangular length=circumference ÷ 2-width
The width of the rectangle==circumference ÷ 2-long
The circumference of the square=side length × 4 letters: C=4a
Side length of the square=circumference ÷ 4
xxUnit 8 Initial understanding of scores
The meaning of the score: divide an object (or the whole) into several parts equally, indicating the number of such one or several points, called the score.
Score comparison size:
1. The molecules are the same, and the smaller the denominator, the larger the value.
2. The denominator is the same, the larger the numerator, the larger the value.
Simple calculation of scores:
Add and subtract the same denominator score: the denominator is unchanged, and the numerator is added and subtracted.
There is a remainder of division
Calculate the division with the remainder:
1. Which one is enough to write on.
2. The remainder must be less than the divisor.
Dividend=quotient × divisor + remainder
Quantity relationship formula:
Number of copies × number of copies=total unit price × quantity=total price speed × time=distance
Total ÷ Copies=Number of Copies Total Price ÷ Quantity=Unit Price ÷ Time=Speed
Total ÷ Per copy=Number of copies Total price ÷ Unit price=Quantity Distance ÷ Speed=time
Work efficiency × working time=total work size - small=difference
Total work ÷ working time=work efficiency large - phase difference=small
Total work ÷ work efficiency=working time small + difference=large