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Mental Math Activities: Estimating and Rounding

written by: Margo Dill • edited by: Elizabeth Wistrom • updated: 3/2/2012

In most school's math curriculum, your child will learn mental math skills. These mental math activities often focus on estimating and rounding large numbers to easily add, subtract, multiply, or divide without using paper and pencil. You can practice these skills with your child.

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    Rounding Skills

    In elementary school, children do mental math activities such as rounding numerals to the nearest ten, hundred, thousand, and so on. Teachers will instruct your child on using mental math skills in real life, such as when shopping to figure out if they have enough money to buy something or when trying to divide a large amount of items among a few people. These mental math problems usually start with rounding, and you can practice this at home with your child.

    If your child is just learning how to round numbers without paper and pencil, then you will want to work one-on-one with your child and focus on one place value at a time. For example, you would give your child several numbers such as 75, 27, 32, and so on. Your child would round all of these to the nearest ten. You should also ask your child to explain why he rounded 75 to 80. Once he has mastered rounding with one-on-one mental math activities, then you can use these skills in the real world.

    Some good places to practice rounding numbers is the grocery store, restaurants, or mall or while reading the newspaper or planning a party. For example, if you are at the grocery store with your child, you can ask him to round the prices of your items to the nearest dollar.

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    Estimating Skills

    Mental math activities practicing estimation skills are more involved than rounding activities. For example, you could work with your child on adding several 3-digit numbers together without paper and pencil by first rounding the numbers to the nearest hundred and then adding them together. You can also talk to your child about real life situations when they would use estimation. For example, they go to a baseball game and want to buy some food at the concession stand. They have $12.00. They can use rounding and estimating to figure out if they have enough money to buy a hot dog, popcorn, soda, and cotton candy without using paper or pencil or a calculator.

    Once you have practiced the mental skills at home one-on-one, then allow children to use their estimation skills at a restaurant to figure out about how much your bill will be before it comes. You can ask your child to use estimating to see how much money you'll need to go to the movies on Saturday.

    Estimating skills can also be used to figure out how much of something you'll need to buy or use, and you can get your child involved in real life mental math activities to practice these skills. Let's say you are having a bar-be-que and inviting 15 people over. At the store, you and your child estimate how much food, paper products, and beverages to buy based on how many items come in each package. When the bar-be-que is over, discuss with your child how well you estimated by looking at anything leftover or that you ran out of, so your child can improve his skills from this experience.

    Mental math activities work best when they are taught one-on-one at home and then practiced in real life situations with parental guidance.