This post is part of a series of standardized test prep posts.
Here is a really simple trick that lets you quickly eliminate wrong answers on multiple choice multiplication tests!
Check just the ones digits in the problem. Multiply quickly in your head, and you will know what the ones digit must be in the correct answer. Cross off answers that don’t have the correct ones digit.
For example, if you are multiplying 57 X 48, you know that 7 X 8 = 56 (multiplying the ones digits of both numbers). The ones digit is 6. So the correct answer to the problem MUST have 6 as the ones digit.
Save a lot of time by trying your new skill before you solve a multiplication problem on a standardized test!
Example: 486 X 592 = ____
Strategy: What must be in the ones place?
#1: The answer MUST be an EVEN number, because both numbers are EVEN (I teach my students they can look at just the number in the ones place to determine if a number is even or odd). Cross off answers c and d because they are odd numbers.
#2: The answer MUST END in 2, because 6 X 2 = 12, which puts 2 in the ones place. Cross off answer a because 6 is in the ones place.
Result: Only answer b can be correct.
There! You have the correct answer without taking the time to solve a complex long multiplication problem! You also can use the method “What Must Be in the Ones Place?” to quickly eliminate wrong answers to multiple choice problems using other operations: addition, subtraction and division.