Unit 1 · Patterns and Sequences
Jamal's Alternating Rules — Work Backwards from 8451
Lesson 6 of 7
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About this lesson
Two alternating rules: −100 then +10, repeated. Work backwards from the 6th term by applying the inverse of each rule in reverse order.
Chapters
0:00Introduction
0:23The Question
1:09Mapping the Sequence and Operations Forward
1:35Reversing the Path (Applying Inverse Operations)
2:02Calculating the Step Values Backward
2:52Exam Strategy — The Net Operation Shortcut
3:32Confirming the Final Choice
Question
Jamal makes a number sequence. He chooses the 1st number in the sequence.
Then he follows these two rules, one after the other, repeatedly:
- Subtract 100 to get the next number in the sequence.
- Add 10 to get the next number in the sequence.
The 6th number in the sequence is 8451.
What is the 1st number in Jamal's sequence?
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