Multiplication

The last thing that the MRI technician said to me before leaving the room was: don’t move. “Don’t move”, piece of cake … or so I thought!

Within moments of listening to the ear-plug muted rumblings of the machine I found myself being lulled into a semi-conscious state. Like a student nodding off in a boring lecture, I began the vicious cycle of stupor then jerking myself awake, stupor … awake. Oh crap, I thought, if I don’t find some way of staying awake I’m going to have to go through all of this again.

Frantically recalling what Meg did in A Wrinkle in Time to save her from control of IT, I began to recite the multiplication tables in my head. I started with nine (I just like nine). 9 x 1 = 9 … I quickly blew through to 9 x 10 = 90. This ain’t gonna cut it — too easy. 9 x 11 = 99, 9 x 12 = 108, 9 x 13 = ... crap! Grade school multiplication tables only went up to tweleve. I could just add nine to one-oh-eight and cheat my way along. But what if I got to 9 x 100 and I didn’t get nine-hundred due to cumulative error? What would my friends think? My mother and her weak heart, it might just kill her to find out! There has to be a better way.

We’re going to have to do this the long way:

13
x 9
----
27
+ 9
----
117

Now why do we do this whole “multiply by the ones and write down the result and then multiply by the tens and write that down shifted over one” nonesense? There has to be a simple answer but no one bothered to tell me!

Rewriting the multiplication in a more linear form we get:

(9)(13) = 117

But thirteen can be written as a sum:

(9)(3 + 10)

Bringing in the distributive law of multiplication:

(9)(3) + (9)(10)

Simplifies to:

27 + 90

Ah ha! I recalled one of my grade school teachers saying that you can put a zero in that “shifted over” spot.

13
x 9
----
27
+ 90
----
117

That makes the two statements identical! This is pretty obvious when you think about it. Since we’re taught the mechanics and not the theory it’s just all taken for granted.

By the time I worked through all of this (as well as some other interesting tidbits involving nine that I will write up later) the technician was rolling me out of the bowels of the great machine. I made it!

(After the fact I did recall that it was IT that was trying to gain control over Meg by forcing her to recite the multiplication tables and was therefore the worst thing that I could have done but it had saved me. Thank you Madeleine L’Engle!)

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