Question 15
MediumOriginal questionFind the missing number: .
Show the answer and explanation
CorrectNot quiteAnswer C
Correct answer: C
Explanation
First simplify the known part: .
So , which gives .
Hence .
Worth noting
Subtracting 12 instead of adding it back gives . To undo a subtraction you add.
- Concept
- Undoing operations to find a missing number
- Typical timeTypical
- 60 s
- Your timeYours
- —
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Ten questions from Simplification & Approximation, at your own pace.