Rewrite the base: the SAT math trap
Short answer: Write 9 as 3². Then 9x = (3x)². Square, don't double.
The trap, in one question
If 3x = 5, what is the value of 9x?
Tempting answer: 10 (just doubled it)
Correct answer: 25 (9x = (3x)2 = 52)
Watch it in under a minute
How to spot it in 3 seconds
Write 9 as 3². Then 9x = (3x)². Square, don't double.
FAQ
What is the rewrite the base trap on the SAT?
Example: If 3x = 5, what is the value of 9x? The tempting answer is 10 (just doubled it); the correct answer is 25 (9x = (3x)2 = 52).
How do you avoid the rewrite the base trap?
Write 9 as 3². Then 9x = (3x)². Square, don't double.
More Math traps
M1Percent of a percentM2Average speedM4Dividing by x deletes a solutionM5Answer the question they asked
← Average speed · Dividing by x deletes a solution →
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