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QUANTITATIVE REASONING · GMAT-Q-PAR-01
Parity, Signs and Consecutive Integers
GMAT lesson development preview · DRAFT · Original learning and assessment material
Concepts and problem-solving strategy
Product of consecutive integers
Signs of products
Think Like a GMAT Test-Taker
Check even/odd and sign restrictions before expanding algebra.
Faster Methods
Use n=2k or n=2k+1 to prove parity.
Count negative factors to determine product sign.
For consecutive integers, factor before multiplying.
Worked example 1
Show that two consecutive integers have an even product.
Exactly one of the consecutive integers is even.
Worked example 2
What is the sign of a product of five negative factors?
An odd number of negative factors makes a negative product.
Common Traps
- Zero is even but neither positive nor negative.
- Odd plus odd is even.
- A negative base to an even power yields a positive result.