Answer: Analysis: It is required that the sum of three numbers in horizontal and vertical rows is 1 1, then the lower half of 1 and 3 is1-1-3 = 7, and the right half of 2 and 3 is/kloc-0.

(2) Fill in the numbers so that the sum of three numbers in each row is 15.

Answer: Analysis: If the sum of three numbers in each row is 15, then 15-6-3=6 between 6 and 3,15-3-8 between 3 and 8, and15-6-8 = 4 between 6 and 8.

2. Fill in 1, 2, 3, 4 and 5 in the circle below, and meet the following conditions respectively.

Analysis: The most important thing in this question is the middle circle, because 1 time has been added in both horizontal and vertical rows, that is, * * has been added twice, and 1 time has been added in others, and the title requires that the numbers cannot be reused, so it is very important to find out the numbers filled in the middle circle and then find out the numbers filled in other circles by enumeration.

(1) All the numbers in the horizontal and vertical circles add up to 8.

Answer: analysis: both the horizontal and vertical lines are equal to 8, so the sum of the two lines is 16, but all the numbers are added together, which is 1+2+3+4+5= 15, which means that 1 is too much, and the middle number is counted twice, so the middle number is counted twice.

(2) Make the numbers in the horizontal and vertical circles add up to 9.

Answer: analysis: both horizontal and vertical rows are equal to 9, so the sum of the two rows is 18, but all the numbers add up to 1+2+3+4+5= 15, which means that 3 is too much, and the middle number is counted twice, so the middle number is 3, leaving 6. According to the enumeration method, 6 =

(3) Make the figures of horizontal circle and vertical circle add up to 10.

Answer: analysis: both the horizontal and vertical lines are equal to 10, so the sum of the two lines is 20, but all the numbers are added together, which is 1+2+3+4+5= 15, that is to say, the middle number is calculated twice, so the middle number is 5, and the rest is 5, according to the enumeration method.

(graphic count)

Knowledge points: There are many ways to count numbers, such as enumeration, marksmanship, formula, numbering and classification. Today's homework focuses on classification, that is, numbers from small to large. Pay attention to all kinds of situations, count them in a certain order, and make sure not to miss a catty.

1. Count the triangles in the picture below.

Answer: (1) 2 small triangles, 1 large triangle (composed of 2 small triangles), ***2+ 1=3 (triangle).

(2) There are four small triangles, four large triangles (consisting of two small triangles), and ***4+4=8 triangles.

(3) There are three small triangles, 1 middle triangle (composed of two small triangles), 1 large triangle (composed of three small triangles), ***3+ 1+ 1=5 (triangle).

2. Count the squares in the picture below.

Answer: (1) 4 small squares, 1 middle squares (composed of 4 small squares), 1 large squares, * * * 4+ 1 = 6 (squares).

(2) There are 1 large, medium and small squares, * * * 1+ 1 = 3 squares.

(3) 4 small squares, 3 large squares, ***4+3=7 (squares)

3. Count how many rectangles there are in the picture below.

Answer: (1) 4 small rectangles, 4 medium rectangles (consisting of 2 small rectangles) and 3 large rectangles, ***4+4+3= 1 1 (rectangles);

(2) There are 3 small rectangles, 1 middle rectangle (composed of 2 small rectangles), 1 large rectangle (composed of 3 small rectangles), ***3+ 1+ 1=5 (rectangle).

4. Find the number of squares with only one circle.

A: A square with 1 rings contains 1 basic squares, a square with 4 rings contains 4 basic squares, and a square with/kloc-0 contains 9 basic squares, so * * has 1+4+1= 6 (squares).

5. How many squares are there in the graph (1)? How many quadrilaterals and triangles are there in Figure (2)?

Answer: (1) If every face of a cube is a square, there are six squares;

(2) There are three quadrangles and two triangles in the triangular prism.

(counting squares)

Knowledge points: The methods for calculating squares are: (1) layers, which is the simplest method, and the ones that are not pressed by the upper layers are completely exposed, from top to bottom are the first layer, the second layer, the third layer and the fourth layer respectively; (2) the number of rows. So when you encounter the problem of counting squares in the future, remember A, one layer at a time. B, the hidden squares should be counted.