Thursday, May 18, 2006

An Unbelievable Math Problem...and New Math


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Doctor Bean, Stacey, PsychoToddler...get your calculators ready. This one is fun.

Here is a math trick so unbelievable that it will stump you. Who comes up with these things...?

1. Grab a calculator. (you won't be able to do this one in your head)
2. Key in the first three digits of your phone number (NOT the area code)
3. Multiply by 80
4. Add 1
5. Multiply by 250
6. Add the last 4 digits of your phone number
7. Add the last 4 digits of your phone number again
8. Subtract 250
9. Divide number by 2

Do you recognize the answer?

I guess someone's got your number!

$$$$$$$$$$$$$$$$$$$$

My daughter is in third grade. I was in third grade circa 1969.

Math is not her subject. Math was not my subject then, nor is it still today.

She learns new math. I learned old math.

Her logic questions involve adding, subtracting, based on the way the questions read. The questions talk about purchases: purchasing cell phones, purchasing computers, purchasing CD players, purchasing cameras.

My logic questions involved adding, subtracting, based on the way the questions read. The questions talked about purchases: purchasing apples, purchasing grapes, purchasing bananas, purchasing oranges.

As we were working on math the other night, and I came across her logic questions, it hit me: "Ah, that's why they call it NEW MATH." I could just try to imagine my 8-year-old self looking at these questions in 1969 and asking: "What's a CD player, what's a cell phone...?"




11 comments:

cruisin-mom said...

purchasing cell phones, purchasing computers, purchasing CD players, purchasing cameras. (2006 version)

purchasing a princess phone with push buttons instead of a dial, purchasing a sliderule, purchasing an 8 track tape player, purchasing a Kodak instamatic camera. (1969 version)

Elie said...

This is a cute math trick but not really impossible to unravel. What you're really doing in steps 2, 3, 5, and 8 is multiplying the 1st three digits of the phone number by 10000 (250 * 80 / 2). In steps 6, 7, and 9 you're simply adding the last four digits (adding it twice and then dividing by two). Steps 4, 5, and 8 cancel eachother out in terms of the extra 250 (1 * 250 - 250). So what you end up with is a seven digit number equating to your phone number. Simple, really (if you're a math geek like me)!

Ezzie said...

What Elie said. :)

(What, I'm a math geek too...)

torontopearl said...

CM: You REALLY are in tune with 1969, aren't you?

Elie: Can some of your math geekiness rub off on me, please?

Ezzie: *grin*

wanderer said...

I must not be a math geek at all, because the answer I got is 84079.5, which is not my phone number...

:(

Elie said...

Pearl: I doubt it; it never rubbed off on my wife or any of my kids...

C-M: Did people still use slide rules in 1969? I was only eight then but I never needed - or learned how - to use one, much to my dad's chagrin. I'd substitute "adding machine", the father of the pocket calculator, which came into vogue just a few years later.

cruisin-mom said...

Hi Elie: I know my husband, who is a few years older than me, always says he used a slide rule (maybe not exactly in '69 but close enough)...Me? well I never made it past algebra and geometry (just skimmed by), I never learned how to use one. Oh, and thanks for rubbing in that you were only 8 years old in '69 ;)

torontopearl said...

How do you feel now, Randi, when I say that in 1969, Elie and I were BOTH eight years old. I just can't remember if I'm older than him...I think I am. Refresh my middle-aged memory, Elie. My birthday is September 23.

Elie said...

Mine is December 7, Pearl Harbor day (ironic, huh?). So you've got me beat by 2-1/2 months, old timer!

Mirty said...

Sorry, I only do hexadecimal.

Teena said...

We were still playing 45s (remember the thing that went in the middle of them?)!!