Let M be the set of positive integersless than or equal to2000 such that the difference of any two numbers in M is neither 5 nor 8. find the maximum numbers of elements in M
Q. Let M be the set of positive integers less than or equal to 2000 such that the difference of any two numbers in M is neither 5 nor 8. find the maximum numbers of elements in M
Pick Smallest Integer: Let's start by picking the smallest positive integer, which is 1, and add it to set M.
Add Numbers to Set: Now, we can't add 1+5=6 or 1+8=9 to M because the difference between these numbers and 1 is either 5 or 8. So, the next number we can add is 1+6=7.
Identify Pattern: Continuing this pattern, we can't add 7+5=12 or 7+8=15 to M, so the next number we can add is 7+6=13.
Calculate Number of Elements: We notice a pattern: we can add a number to M every 6th integer to avoid differences of 5 or 8. So, we can calculate the number of elements by dividing 2000 by 6.
Check Inclusion of Last Numbers: Dividing 2000 by 6 gives us 2000/6=333 with a remainder of 2. So, we can have 333 elements, and we need to check if we can include the last two numbers, 1999 and 2000.
Verify First and Last Numbers: Since 1999−1994=5 and 2000−1992=8, we can't include 1999 or 2000 in M. So, we stick with 333 elements.
Verify First and Last Numbers: Since 1999−1994=5 and 2000−1992=8, we can't include 1999 or 2000 in M. So, we stick with 333 elements. However, we need to check if the first and last numbers in our set follow the rule. The last number we can include is 1+333×6=1999, but we just determined we can't include 1999.