Going Mental from 4th Grade Math

Who knew that 4th grade math would be so mental? No really, there’s a chapter in my daughter’s book that is labeled: Mental Math. My head hurt that night, trying to mentally grasp the justification of making the parents go crazy trying to help their child understand the grouping, carrying, breaking down, place value of numbers in a way that makes no ‘at first glance’ sense.

Mental math is the main form of calculation used by most people and the simplest way of doing many calculations. Research has shown that in daily life at least 75% of all calculations are done mentally by adults.
— https://www.k-5mathteachingresources.com

In New York City, Common Core Math fundamentals are not as common as what you recall when attending grade school. The 4th grade math that our children are doing is beyond what we or those born earlier than 1980 are familiar with.

Let’s examine this math problem:

Take a minute to solve the same example, the old fashion long division way, do you get the same result? Using mental math, I’m getting a headache still trying to figure out why we are multiplying 6 x 10 = 60 — where did the ten come from? Why are we multiplying it by 6 and then subtracting the answer from 100?

Although we have been introduced to another year of common core math, we were not quite ready for this mental math. If you are also getting a headache, here are some websites that we study to make ourselves seem smart when we are reviewing homework with the 4th grader. The game portion of many of the sites, keeps my daughter focused on something entertaining allowing her to retain the information in the worksheets.

Helpful Websites for Mental Math:

  • YouTube Search - the chapter name of your child’s math book

Some Vocabulary for Mental Math:

  • Addend - Numbers participating in addition.

  • Associative Property of Addition - The property of addition that states- changing the order in which numbers are added, doesn't affect the result of addition.

  • Associative Property of Multiplication - the product of three or more numbers remains the same regardless of how the numbers are grouped. 

  • Distributive Property - Distributive property states that multiplying the sum by a number gives the same result as first multiplying each addend by the number and then adding the products.

Additional common core vocabulary for 4th Grade mental math can be found on Splash Math.


Do you understand 4th grade mental math?

Help me by sending some tips in the comments.