Unit 2 · Number Theory
45, 54, 77, 80, 99 — Which Changes Most?
Lesson 3 of 15
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About this lesson
Five numbers are each rounded to the nearest 10. Which one changes the most? The key is understanding that 'changes the most' means the biggest gap between original and rounded — and that the worst-case change when rounding to the nearest 10 is exactly 5. One of these five numbers achieves that maximum.
Chapters
0:00Introduction
0:23The Question
0:48Defining the evaluation matrix
1:07Evaluating options A and B (45 and 54)
1:38Evaluating options C, D, and E (77, 80, and 99)
2:05Comparing the delta and isolating the maximum
2:28Exam strategy — the midpoint boundary rule
3:18Confirming the final option
Question
If each of these numbers is rounded to the nearest 10, which number changes the most?
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