by Josh Rappaport
Now that we're deep in the heart of summer, I'd like to suggest an enjoyable activity that helps children keep their math skills sharp.
I call this activity "Math Ball." Here's how it works.
First, teach (or review) some mental math shortcuts appropriate for your kids.
Some of the shortcuts I like to use are:
a) To multiply an even number by 5, first take half, then tack on a zero.
i.e.: 18 x 5. half of 18 is 9. Adding a zero gives the answer, 90.
b) To multiply a number by 25, just divide the number by 4,
then tack on two zeros.
i.e.: 32 x 25. 32 ÷ 4 = 8. Tacking on two zeros gives 800.
[Note that this trick works only for perfect multiples of 4.
You can adapt it for other numbers if you have older students.]
c) Multiplying by 11 for two-digit numbers whose digits add to 9 or less.
To multiply such a number by 11, put down its first digit, followed by the sum of its digits, followed by the last digit. i.e. 42 x 11. First digit is 4. Second digit is 6 (4 + 2). Final digit is 2. Answer: 462.
d) Adding 9 to a number. First add 10, then take 1 away.
Thus: 47 + 9 = (47 + 10) – 1 = 57 – 1 = 56
You can also adapt this trick for adding 19, 29, 39, etc.
e) Subtracting 9 from a number. Just subtract 10, then add 1.
Thus: 62 - 9 = (62 – 10) + 1 = 52 + 1 = 53
You can adapt this trick for subtracting 19, 29, 39, etc.
Of course, feel free to modify the math strategies as appropriate. For children learning the basics, you might use problems like 2 + 5. And teens approaching their college years might need to practice trigonometry formulas. Anyhow, whatever type of problems forms the subject matter for your children, the way you play the game remains the same. Here's how it goes.
First, I throw a ball to the child, and as I do I state a math problem of the type that we have just been focusing on. Big bouncy balls tend to be good to use. Beach balls, for example, are great. After the child catches the ball, s/he has to throw the ball back to me while saying the answer.
[NOTE: for children who like soccer — or who just like kicking balls — kicking the ball back and forth works just as well as throwing it.]
If the child gets the answer right, I catch the ball, and I give the child another problem, and play continues in this way, one right answer after another.
But if the child gets an answer wrong, I do something weird. Sometimes I don't catch the ball; I let it go past me, and the child needs retrieve it. Other times I throw it back to the child, but on the ground, and usually a little bit out of the way, not directly back to the child.
The point is that my weird reply tells the child that the answer was wrong, and s/he needs to try again. Usually while the child is chasing down the ball, I'll give a hint. I might even model how to do a similar problem. For example, if the problem the child got wrong was 24 x 11, I might explain how to do 35 x 11.
In any case, the time when the child is retrieving the ball gives her/him a chance to re-think the strategy used and to figure out how to get the right answer. Usually the child gets the right answer the next time.
I realize that some of you may be shaking your heads, thinking, "How mean, to throw the ball in a different direction, or throw it back on the ground." But the funny thing is that children LIKE IT when I do this. They think it is funny, and there's just something about having the ball returned in this weird way that motivates them to want to get the answer right. Some of you may need to actually see this done to believe that kids like it. But if you do, I'm confident that you'll see they enjoy it a lot.
Once children get skilled at the particular math trick you're teaching, turn the game around. Let the child give YOU the math problems, and then it becomes your turn to state the answers. When you do this, it's fun to get the answers wrong on purpose ... from time to time. Kids just love returning the favor by making you go chase the ball.
Anyhow, these are the basic rules for "Mathball." Some children like calling it "Nerdball," too, by the way. They think it's funny in a strange way.
So enjoy "Mathball" or "Nerdball" this summer. Your children won't even realize that they're keeping their math skills sharp, but you'll know that they are. So in the long run, everyone wins at this game.
Josh Rappaport lives and works in Santa Fe, New Mexico, along with his wife and two teenage children. Josh is the author of the Algebra Survival Guide, and the companion Algebra Survival Guide Workbook, both of which will soon be available for homeschoolers as a computer-based Learning Management System, developed and run by Sleek Corp., of Austin, TX.
Now that we're deep in the heart of summer, I'd like to suggest an enjoyable activity that helps children keep their math skills sharp.
I call this activity "Math Ball." Here's how it works.
First, teach (or review) some mental math shortcuts appropriate for your kids.
Some of the shortcuts I like to use are:
a) To multiply an even number by 5, first take half, then tack on a zero.
i.e.: 18 x 5. half of 18 is 9. Adding a zero gives the answer, 90.
b) To multiply a number by 25, just divide the number by 4,
then tack on two zeros.
i.e.: 32 x 25. 32 ÷ 4 = 8. Tacking on two zeros gives 800.
[Note that this trick works only for perfect multiples of 4.
You can adapt it for other numbers if you have older students.]
c) Multiplying by 11 for two-digit numbers whose digits add to 9 or less.
To multiply such a number by 11, put down its first digit, followed by the sum of its digits, followed by the last digit. i.e. 42 x 11. First digit is 4. Second digit is 6 (4 + 2). Final digit is 2. Answer: 462.
d) Adding 9 to a number. First add 10, then take 1 away.
Thus: 47 + 9 = (47 + 10) – 1 = 57 – 1 = 56
You can also adapt this trick for adding 19, 29, 39, etc.
e) Subtracting 9 from a number. Just subtract 10, then add 1.
Thus: 62 - 9 = (62 – 10) + 1 = 52 + 1 = 53
You can adapt this trick for subtracting 19, 29, 39, etc.
Of course, feel free to modify the math strategies as appropriate. For children learning the basics, you might use problems like 2 + 5. And teens approaching their college years might need to practice trigonometry formulas. Anyhow, whatever type of problems forms the subject matter for your children, the way you play the game remains the same. Here's how it goes.
First, I throw a ball to the child, and as I do I state a math problem of the type that we have just been focusing on. Big bouncy balls tend to be good to use. Beach balls, for example, are great. After the child catches the ball, s/he has to throw the ball back to me while saying the answer.
[NOTE: for children who like soccer — or who just like kicking balls — kicking the ball back and forth works just as well as throwing it.]
If the child gets the answer right, I catch the ball, and I give the child another problem, and play continues in this way, one right answer after another.
But if the child gets an answer wrong, I do something weird. Sometimes I don't catch the ball; I let it go past me, and the child needs retrieve it. Other times I throw it back to the child, but on the ground, and usually a little bit out of the way, not directly back to the child.
The point is that my weird reply tells the child that the answer was wrong, and s/he needs to try again. Usually while the child is chasing down the ball, I'll give a hint. I might even model how to do a similar problem. For example, if the problem the child got wrong was 24 x 11, I might explain how to do 35 x 11.
In any case, the time when the child is retrieving the ball gives her/him a chance to re-think the strategy used and to figure out how to get the right answer. Usually the child gets the right answer the next time.
I realize that some of you may be shaking your heads, thinking, "How mean, to throw the ball in a different direction, or throw it back on the ground." But the funny thing is that children LIKE IT when I do this. They think it is funny, and there's just something about having the ball returned in this weird way that motivates them to want to get the answer right. Some of you may need to actually see this done to believe that kids like it. But if you do, I'm confident that you'll see they enjoy it a lot.
Once children get skilled at the particular math trick you're teaching, turn the game around. Let the child give YOU the math problems, and then it becomes your turn to state the answers. When you do this, it's fun to get the answers wrong on purpose ... from time to time. Kids just love returning the favor by making you go chase the ball.
Anyhow, these are the basic rules for "Mathball." Some children like calling it "Nerdball," too, by the way. They think it's funny in a strange way.
So enjoy "Mathball" or "Nerdball" this summer. Your children won't even realize that they're keeping their math skills sharp, but you'll know that they are. So in the long run, everyone wins at this game.
Josh Rappaport lives and works in Santa Fe, New Mexico, along with his wife and two teenage children. Josh is the author of the Algebra Survival Guide, and the companion Algebra Survival Guide Workbook, both of which will soon be available for homeschoolers as a computer-based Learning Management System, developed and run by Sleek Corp., of Austin, TX.
At his blog, Josh writes about math education, offering tips and tricks. Josh also authors Turtle Talk, a free monthly newsletter with an engaging "Problem of the Month." You can see a sample issue here or subscribe at this site. Josh also is co-author of the "learn-by-playing" Card Game Roundup books, and author of PreAlgebra Blastoff!, a "Sci-Fi" cartoon math book featuring a playful, hands-on approach to positive and negative numbers.
In the summer Josh leads workshops at homeschooling conferences and tutors homeschoolers nationwide using SKYPE. Contact Josh by email @ josh@SingingTurtle.com or follow him on Facebook, where he poses two fun math Qs/day.
