Unit 6 · Algebra
Factorise 12×35 → ▲ = 15
Lesson 7 of 12
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About this lesson
12 × 35 = 4 × ▲ × 7. What is ▲? Two elegant approaches: (1) compute 12 × 35 = 420, simplify RHS to 28▲, divide to get 15. (2) Factor — 12 = 4 × 3 and 35 = 5 × 7, so LHS = 4 × 3 × 5 × 7; cancel the 4 and 7 that appear on both sides, leaving ▲ = 3 × 5 = 15. Method 2 is the elegant OC-level approach.
Chapters
0:00Introduction
0:26The Question
0:56Analyzing the Left Side of the Equation
1:20Recombining the Left Side Factors
1:47Solving via Common Multipliers
2:12Confirming the Answer Choice
2:30Correct answer
Question
12 × 35 = 4 × ▲ × 7
What is the missing number ▲?
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