Unit 2 · Number Theory

8 → 9 in Five Numbers — Biggest Increase?

Lesson 5 of 15

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Replace the digit 8 with 9 in each of five numbers — which increases the most? The answer is whichever number has 8 in the highest place value position. In 81 234, the 8 is in the ten-thousands place, so replacing it adds 10,000. Students who read the numbers carefully rather than choosing the largest-looking option get this right every time.

Chapters

0:00Introduction
0:21The Question
0:52Unpacking the substitution rule
1:19Evaluating options A, B, and C
1:49Evaluating options D and E
2:19Exam strategy — the highest column position rule
3:25Confirming the final option

Question

When the digit 8 is replaced by the digit 9 in each of the numbers below, which number increases the most?

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