How to Estimate Multiplication Problems
Estimating multiplication problems is a handy technique for checking your work and solving math problems quickly. Here are a few ideas to help you master estimation using rounding and mental math!
How to Estimate with Multiplication
Decimals
Rounding makes math problems easier to estimate. For example, let's estimate the answer to the problem 3.4 x 8.8. Start by rounding the decimals to the nearest whole number. Numbers with a decimal value of 0.5 or higher are rounded up, and numbers with a decimal value of 0.4 or lower are rounded down. If we follow this rule, 3.4 can be rounded down to 3, and 8.8 can be rounded up to 9.
Next, you'll simply multiply the two resulting numbers together. Since 3 x 9 = 27, that's your estimated answer. Compared to the exact answer, 29.92, the estimate was fairly close.
Whole Numbers
When you're estimating multiplication problems with whole numbers, round each number in the problem to another whole number that's easier to multiply mentally. For example, if you have the problem 54 x 97, you can round the 54 down to 50 the 97 up to 100. This gives you 50 x 100, which you can solve in your head.
Since 10 x 10 = 100, then 50 x 100 = 50 x 10 x 10. You can find the product of any number and 10 by simply adding a 0 to the other number, so 50 x 10 = 500 and 500 x 10 = 5,000. This means the estimated answer is 5,000. If you check this answer using a calculator, you'll find that 54 x 97 = 5,238, so this estimate is fairly close.
Mixed Problems
Let's look at the problem 3.4 x 89. The first thing we need to do is round 3.4 to the nearest whole number, which is 3. Next, we'll round 89 to the nearest ten, which gives us 90. Since 9 x 10 = 90, you can turn this problem into 3 x 9 x 10. You already know that 3 x 9 = 27, and you can find the answer to 27 x 10 by adding a 0 to get 270. Then, check your answer using a calculator. You'll see that the exact answer is 302.6, which is reasonably close to 270.
Summing Up
These examples give you a sense of how rounding and using mental math can be great tools for quickly estimating answers; however, estimation won't produce exact solutions. Remember that estimating with numbers that are as close as possible to the original numbers in the problem will give you the best possible result. It's also helpful to keep in mind that if you round both numbers in the multiplication problem up, the estimate will be high, and if you round them both down, it will be low.
Other Articles You May Be Interested In

This sample worksheet shows you how to structure both basic and advanced multiplication tables. These formats are meant to help students memorize simple multiplcation problems and, when randomized, challenge them.

Here are some ways to help your child learn multiplication and make fourth grade math homework fun.
We Found 7 Tutors You Might Be Interested In
Huntington Learning
 What Huntington Learning offers:
 Online and incenter tutoring
 One on one tutoring
 Every Huntington tutor is certified and trained extensively on the most effective teaching methods
K12
 What K12 offers:
 Online tutoring
 Has a strong and effective partnership with public and private schools
 AdvancEDaccredited corporation meeting the highest standards of educational management
Kaplan Kids
 What Kaplan Kids offers:
 Online tutoring
 Customized learning plans
 RealTime Progress Reports track your child's progress
Kumon
 What Kumon offers:
 Incenter tutoring
 Individualized programs for your child
 Helps your child develop the skills and study habits needed to improve their academic performance
Sylvan Learning
 What Sylvan Learning offers:
 Online and incenter tutoring
 Sylvan tutors are certified teachers who provide personalized instruction
 Regular assessment and progress reports
Tutor Doctor
 What Tutor Doctor offers:
 InHome tutoring
 One on one attention by the tutor
 Develops personlized programs by working with your child's existing homework
TutorVista
 What TutorVista offers:
 Online tutoring
 Student works oneonone with a professional tutor
 Using the virtual whiteboard workspace to share problems, solutions and explanations