Wild About Math!

How fast can you do mental Math?

There’s an interesting web-site, brainetics.com, that is all about doing mental Math quickly. I have to confess that while I know quite a few mental Math tricks and while I’ve written quite a number of posts and made several videos about mental Math tricks I’m not particularly fast at applying these tricks. Doing Math quickly in one’s head is all about knowing techniques, having a strong memory and maintaining focus. I know techniques. Memory and focus are currently a challenge for me.

Brainetics sells a $180 product geared to improving mental Math abilities. I’m not rushing to spend $180 to see how helpful Brainetics might be but I’d love feedback from anyone who has used the product.

A free resource on the Brainetics site is the Brain Games page. Near the bottom of the page is a link to a game, Brain Burst. The game has two levels, hard and harder. The first level gives you a bunch of two-digit by two-digit multiplication problems. Possible answers are floating on the screen. You get points for clicking on the right answer quickly. You lose points for wrong clicks. If you are slow to answer then incorrect choices start to disappear, making it easier to get the right answer but, I imagine, losing you points.

My highest score was 29 points on the “All Star” level, which is the easiest of the two. I suspect many of you could do better. I found that racing against the clock was mentally stressful even though I know how to do 2×2 digit multiplications in my head. Brainetics may have a better approach than I have to this kind of multiplication or they may have a good approach to holding the partial product in your head while you work on more of the product.

If you want to try this game and don’t have an approach to mental multiplication I suggest this for the 2×2 digit case:

To multiply numbers with digits ab and cd together:

1. Multiply bxd. That’s the last digit. There may be a carry you’ll have to remember.
2. Multiply adxbc and add the carry to get the next digit. You may generate a new carry.
3. Multiply axc and add the carry to get the rest of the answer.

As an example, to multiply 12×34:

1. 2×4 = 8. 8 is the last digit.
2. 1×4 + 2×3 = 10. 0 is the next digit. 1 is the carry.
3. 1×3 = 3. Add the carry of 1. 4 is the leftmost digit of the answer.
4. 408 is the answer.

I found myself using the strategy of guesstimating answers. That helped sometimes, although sometimes two of the possible answers were close to one another.

I’d be interested to know how others do with this game? Do we have brilliant mental mathemagicians among us?

If you’re interested in learning more mental Math tricks check out my related articles and videos:

• How to square large numbers quickly (part 1)
• Impress your friends with mental Math tricks
• Quick multiplication by 12: A gentle introduction to Trachtenberg speed mathematics
• The algebra of cross-multiplication
• Mental Math magic by Arthur Benjamin
• Vedic multiplication using bases: an introduction
• The first ever Wild About Math! mathcast
• Mathcast #2: Quick multiplication of two 2-digit numbers
• Mathcast #3: Quick multiplication of two 3-digit numbers
• Mathcast #4: Quick squaring of 2-digit numbers

Also, check out a couple of Dave Marain’s recent explorations on mental Math at his MathNotations blog:

• A Much Harder Mental Math ‘Trick’?? - Algebra May Not Be Optional!
• 508^2 = 258,064: Invent your own Mental Math ‘Trick’ and Prove It!

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