Odd and even follow fixed rules under addition and multiplication. Positive and negative follow fixed rules under multiplication and division. You can answer some ACT items from the sign or the parity without computing the whole number. Integers more broadly are in integers on ACT Math.
Odd and even
Even plus even is even. Odd plus odd is even. Even plus odd is odd. Even times anything whole is even. Odd times odd is odd. If a question says “which must be even,” test one even and one odd instead of expanding an expression. Factors and multiples use the same integers, in factors, multiples, LCM, and GCF.
Positive and negative
A negative times a negative is positive. A negative times a positive is negative. An even number of negative factors is positive. An odd number is negative. Absolute value strips the sign. That operation is in absolute value. Exponents, which repeat the sign rule, are in exponent rules.
The bottom line
Track parity for even and odd. Count the negative signs for the sign of a product. Do the full arithmetic only if the choices still disagree.
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This article offers general ACT prep guidance. The ACT can change from year to year, including its format, scoring, policies, test dates, and fees, so always confirm the latest details on the official ACT website at act.org before you make decisions. ACT® is a registered trademark of ACT, Inc. thirty-six is not affiliated with, endorsed by, or sponsored by ACT.