Math Problem Statement

How many numbers between 1 and 2022 inclusive are not divisible be neither 3, nor 5, nor 7?

Solution

To find the number of integers between 1 and 2022 that are not divisible by 3, 5, or 7, we'll use the principle of Inclusion-Exclusion.

Step 1: Calculate the number of integers divisible by each number

  1. Divisible by 3: The number of integers divisible by 3 between 1 and 2022 is: 20223=674\left\lfloor \frac{2022}{3} \right\rfloor = 674

  2. Divisible by 5: The number of integers divisible by 5 between 1 and 2022 is: 20225=404\left\lfloor \frac{2022}{5} \right\rfloor = 404

  3. Divisible by 7: The number of integers divisible by 7 between 1 and 2022 is: 20227=288\left\lfloor \frac{2022}{7} \right\rfloor = 288

Step 2: Calculate the number of integers divisible by combinations of two numbers

  1. Divisible by 3 and 5 (LCM = 15): 202215=134\left\lfloor \frac{2022}{15} \right\rfloor = 134

  2. Divisible by 3 and 7 (LCM = 21): 202221=96\left\lfloor \frac{2022}{21} \right\rfloor = 96

  3. Divisible by 5 and 7 (LCM = 35): 202235=57\left\lfloor \frac{2022}{35} \right\rfloor = 57

Step 3: Calculate the number of integers divisible by all three numbers

  1. Divisible by 3, 5, and 7 (LCM = 105): 2022105=19\left\lfloor \frac{2022}{105} \right\rfloor = 19

Step 4: Apply the principle of Inclusion-Exclusion

The total number of integers between 1 and 2022 that are divisible by 3, 5, or 7 is: Ndiv=(674+404+288)(134+96+57)+19=1366287+19=1098N_{\text{div}} = (674 + 404 + 288) - (134 + 96 + 57) + 19 = 1366 - 287 + 19 = 1098

Step 5: Subtract from the total number of integers

The total number of integers between 1 and 2022 is: 20221+1=20222022 - 1 + 1 = 2022

Thus, the number of integers between 1 and 2022 that are not divisible by 3, 5, or 7 is: 20221098=9242022 - 1098 = 924

So, 924 numbers between 1 and 2022 are not divisible by 3, 5, or 7.

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Related Questions:

  1. How many numbers between 1 and 2022 are divisible by either 3, 5, or 7?
  2. How many numbers between 1 and 2022 are divisible by 2, 3, or 5?
  3. What is the sum of all numbers between 1 and 2022 that are divisible by 3?
  4. How many numbers between 1 and 1000 are not divisible by 4, 6, or 9?
  5. How many numbers between 1 and 2022 are divisible by exactly two of the numbers 3, 5, or 7?

Tip: The principle of Inclusion-Exclusion is a powerful tool to calculate the size of the union of multiple sets, especially when dealing with divisibility problems.

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Math Problem Analysis

Mathematical Concepts

Number Theory
Inclusion-Exclusion Principle
Divisibility

Formulas

-

Theorems

Inclusion-Exclusion Principle

Suitable Grade Level

High School