Autumn and Winter ** Counterattack Guide
Mathematical thinking clearance
Grade 4 Lecture 6 Repulsion Principle 2 Three-quantity overlapping problem
Three-quantity overlap problem: If there are three categories of A, B, and C to be counted, then the sum of the number of elements in class A, class B, and class C = the number of elements in class A + the number of elements in class B + the number of elements in class C - the number of elements in both class A and class C - the number of elements in both class A and class C + the number of elements in class A and class B and class C. （a∪b∪c = a+b+c - a∩b - b∩c - c∩a + a∩b∩c）
1. The whole class is interested in at least one of the three subjects of Chinese, mathematics and English, of which 30 people like Chinese, 32 people like mathematics, 21 people like English, 15 people like Chinese and 15 people like mathematics, 14 people like mathematics and English, 12 people like Chinese and English, and 8 people like all three, so ask for the total number of students in the class.
Grade 4 Lecture 6 Repulsion Principle 2 - Three-Quantity Overlapping Problem (1).Mathematical thinking clearance
Grade 4 Lecture 6 Repulsion Principle 2 Three-quantity overlapping problem
2. Find out how many natural numbers within 100 are not multiples of any number?
Grade 4 Lecture 6 The Repulsion Principle 2 - Three-Quantity Overlapping Problem (2) Related Reading:
Grade 4 Lecture 5 Principle of Repulsion 1 - Overlapping Problem of Two Quantities.
Grade 4 Lecture 4 Basic Methods of Counting - Principles of Multiplication Lecture 3 Basic Methods of Counting - Principles of Addition.