Page 20 - NUMINO Challenge_B2
P. 20
Basic Concepts Sum of Grouped Numbers
The calendar below shows the month of November. The sum of the eight
colored numbers can be found in various ways.
Sun Mon Tue Wed Thu Fri Sat
12345
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
As shown in the figure on the right, there are four pairs of
numbers that are opposite each other. The sum of each
pair is 20. Since there are four pairs, the sum of the eight
numbers is 20 4 80.
Match the four pairs of numbers that are opposite each other. Make the
two numbers in each pair equal by subtracting a number from the greater
number and adding it to the smaller number. Since all eight numbers
become 10, their sum is 10 8 80.
Example The sum of seven numbers in a colored shape as below is 266.
Which is the greatest of the seven numbers?
Class Notes 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
If you make the two numbers opposite each other equal, the sum of the seven colored
numbers will become the same as adding , the number in the center, 7 times.
11 7
9
2 3 4 13 22 23 24
10
If the number in the center is , the sum of the seven numbers is Therefore,
the number in the center is 266 7
The greatest number is always greater than the number in the center by 11.
Therefore, 11 .
17Number and Operations
The calendar below shows the month of November. The sum of the eight
colored numbers can be found in various ways.
Sun Mon Tue Wed Thu Fri Sat
12345
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
As shown in the figure on the right, there are four pairs of
numbers that are opposite each other. The sum of each
pair is 20. Since there are four pairs, the sum of the eight
numbers is 20 4 80.
Match the four pairs of numbers that are opposite each other. Make the
two numbers in each pair equal by subtracting a number from the greater
number and adding it to the smaller number. Since all eight numbers
become 10, their sum is 10 8 80.
Example The sum of seven numbers in a colored shape as below is 266.
Which is the greatest of the seven numbers?
Class Notes 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
If you make the two numbers opposite each other equal, the sum of the seven colored
numbers will become the same as adding , the number in the center, 7 times.
11 7
9
2 3 4 13 22 23 24
10
If the number in the center is , the sum of the seven numbers is Therefore,
the number in the center is 266 7
The greatest number is always greater than the number in the center by 11.
Therefore, 11 .
17Number and Operations
