You’re at the grocery store and you remember that you promised to make spaghetti for a family reunion. Happily, you notice a sale on pasta: buy three, get the fourth one free. Each box costs $0.99. You have $10 left in your grocery budget. How many boxes of spaghetti will you be able to get for the reunion?
Have you ever been in a situation like that? Most likely, yes. We are often called upon to do mental math in everyday life. And it seems like the more familiar you are with the process, the less intimidating it is.
Charlotte Mason included mental math in her students’ lessons regularly. The math lesson time was focused on whatever new concept was being introduced or solidified, but the final five minutes or so of every math lesson was devoted to mental math. The teachers would verbally present interesting scenarios that required the students to do mental calculations with math concepts they had already learned.
But the mental math sessions were more than just a review technique. That five-minute touch each day reinforced the habit of attention, for it required the students to listen carefully and remember details. It also encouraged the students in the habit of imagination: the skill of accurately picturing in your mind’s eye something as it is being described.
The teachers were careful to paint verbal scenarios that would hold meaning for the students and peak their interest. Such scenarios could be as simple or as complicated as needed, but always interesting. Here is an example that demonstrates how one scenario can grow gradually more difficult.
Walking down the street there is a policeman, a dog, and a butcher’s boy. How many creatures? Why?
How many legs? Why?
How many more legs than tails were there in the street? Why?
You could stop at any point in that sequence, depending on which math concepts the student has mastered. The Why? is given because we want to always require the student to give a fully-worded answer that explains the entire equation. So the answers to those questions might sound like this.
There are three creatures, because one policeman plus one dog plus one boy equals three.
The boy and the man had two legs, the dog four, so that though there were only three creatures there were eight legs.
Only the dog had a tail, so given eight legs and one tail, there were seven more legs than tails in the street.
You can easily see how such interesting scenarios are one way that Charlotte kept math a “living” subject. Most importantly, those mental math sessions gave the students practice in thinking mathematically. Every day.
You can give your students the advantage of that kind of practice every day too. Just take five minutes at the close of each math lesson to do mental math. Set aside the books and present verbal scenarios that review math concepts your student has already mastered. Be sure to incorporate people, places, and events that are of interest to your child and have fun!
You may be surprised at how readily your children will take to this activity and find it enjoyable. They may start creating their own mental math scenarios just for fun as they ride along in the van or sit around the lunch table!
Mental math does not have to be hard or complicated to be effective. Keep it interesting. Keep it regular. Keep it enjoyable! And your children will grow confident and comfortable in thinking mathematically.
Note: Mental math examples taken from Mathematics: An Instrument for Living Teaching by Richele Baburina.