Unit 2 · Number Theory
Multiples of 3 — But Not 8
Lesson 11 of 18
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About this lesson
Count multiples of 3 up to 100 (there are 33), then subtract those that are also multiples of 8 — which means multiples of LCM(3, 8) = 24. There are 4 of those, so the answer is 33 − 4 = 29.
Chapters
0:00Introduction
0:21The Question
0:51Finding the Total Multiples of 3
1:19Identifying the Overlapping Multiples
1:54Calculating the Final Filtered Count
2:17Exam Strategy — The Common Multiple Exclusion
2:50Confirming the Final Option
Question
How many whole numbers between 1 and 100 are multiples of 3, but are not multiples of 8?
You should include 3 itself.
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