Unit 1 · Patterns and Sequences

2×P − 4 = 36 — What Comes Before 36?

Lesson 5 of 6

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A sequence rule says each number is 4 less than double the previous. Jasper needs the number directly BEFORE 36, then adds its digits. The two-step trap: you must reverse the rule (work backwards from 36), not apply it forward. Option E (14) is what you get if you apply the rule forward to 36 — a classic direction error.

Chapters

0:00Introduction
0:21The Question
0:55Modeling the forward rule algebraically
1:26Inverting the operations to trace backwards
1:57Executing the backwards calculation
2:23Summing the target digits
2:48Exam strategy — the step-by-step forward verification
3:34Confirming the final option

Question

In a sequence, each number is 4 less than double the previous number.

Jasper finds the number directly before 36 in the sequence.

His answer has two digits. He adds these two digits to get a new number.

What is the new number?

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