Unit 6 · Algebra
3n < 30 & 6n > 40 — Sum All Valid Whole Numbers
Lesson 18 of 24
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About this lesson
3n < 30 means n ≤ 9. 6n > 40 means n ≥ 7. The whole numbers in both ranges are 7, 8, and 9. Their sum is 24.
Chapters
0:00Introduction
0:22The Question
0:58Defining the variables and target goal
1:21Calculating the upper boundary (Clue 1)
1:49Calculating the lower boundary (Clue 2)
2:13Intersecting boundaries to find the integer set
2:46Computing the combined target sum
3:04Exam strategy — consecutive arithmetic symmetry
3:46Confirming the final option
Question
Mateo is thinking of a whole number.
If he multiplies his number by 3, the answer is less than 30.
If he multiplies his number by 6, the answer is greater than 40.
There is more than one number Mateo could be thinking of.
What is the sum of all of the numbers Mateo could be thinking of?
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