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Let's explore the solutions in the Math 4th-grade book on pages 111, 112, 113 of VBT book 2, Focus practice, exercise 172 to easily tackle exercises 1, 2, 3, 4, and 5, reinforcing knowledge so that when encountering similar problems, you can solve them correctly.
Solving 4th-grade math problems on pages 111, 112, 113 of VBT book 2, Focus practice, exercise 172
1. Solve problem 1 - Math exercise book 4th grade book 2 page 111
Problem:
The population of four provinces (according to 2011 data - Wikipedia) is given in the following table:
The names of the provinces in order of population from least to most (in the table above) are:
Solution Method
Compare the populations of the provinces and arrange them in order from least to most populous.
Answer:
The provinces in order of population from least to most are: Ninh Thuận; Hà Giang; Quảng Bình; Cà Mau.
2. Solve problem 2 - Math exercise book 4th grade book 2 page 112
Problem:
Calculate:
Solution Method:
- When the expression involves addition, subtraction, multiplication, and division, perform multiplication and division first, then perform addition and subtraction.
- If the expression involves only addition and subtraction or only multiplication and division, perform the operations from left to right.
Answer:
3. Solve problem 3 - Math exercise book 4th grade book 2 page 112
Problem:
Find x:
Solution Method
Apply the rules:
- To find the subtracted number, add it to the difference.
To find the divided number, multiply the quotient by the divisor.
Answer
4. Solve problem 4 - Math exercise book 4th grade book 2 page 112
Problem:
Find three consecutive natural numbers with a sum of 198.
Solution Method
Because the three numbers are consecutive natural numbers, two consecutive numbers differ by either 1 more or 1 less.
Draw a diagram representing the three numbers, then based on the diagram, find the first number, and then sequentially find the other two numbers.
Answer
As the three numbers are consecutive natural numbers, two consecutive numbers differ by either 1 more or 1 less.
Three times the first number is: 198−(1+1+1)=195
The first number is: 195:3=65
The second number is: 65+1=66
The third number is: 66+1=67
Therefore, three consecutive natural numbers with a sum of 198 are 65, 66, and 67.
Note: Alternatively, it can be solved as follows:
Observation: The average of three consecutive natural numbers is precisely the number in the middle of those three, or specifically the second number.
The second number is: 198:3=66
The first number is: 66−1=65
The third number is: 66+1=67
Therefore, the sum of three consecutive natural numbers is 198, and they are 65, 66, and 67, respectively.
5. Solve problem 5 - Math exercise book 4th grade book 2 page 113
Problem:
In a class of 33 students, the number of male students is equal to 4/7 of the number of female students. How many male students are there in the class?
Solution Method
1. Illustrate: Assume the number of male students as 4 equal parts, then the number of female students as 7 equal parts.
2. Find the total number of equal parts.
3. Determine the value of 1 part by dividing the total sum by the total number of equal parts.
4. Find the number of male students (multiply the value of one part by the number of parts representing the number of male students).
Note: Steps 3 and 4 can be combined into one step.
Answer
According to the diagram, the total number of equal parts is:
11 parts obtained by adding 7 and 4 together.
The class has male students as:
33 divided by 11 times 4 equals 12 (students).
Answer: 12 students.
You are currently viewing the guide for solving 4th-grade math problems on pages 111, 112, 113 of VBT book 2, Concentrated Practice, exercise 172. You can review the instructions for solving 4th-grade math problems on pages 110, 111 of VBT book 2 Reviewing finding two numbers when knowing the sum or difference and the ratio of those two numbers, or preview the instructions for solving 4th-grade math problems on pages 113, 114, 115 of VBT book 2 Concentrated Practice to understand more about the lesson.
