One of the kiddos in the cul-d-sac is in 4th grade and had the following homework question. Her engineer father usually helps with math homework and was scratching his head. Her accountant mother was scratching her head.


I'm an engineer and used to ruin the curve for everyone else in math so I looked at it. It gave me Tourrette's. The real answer is simple but the "new math" is idiotic.

Accounting degree here, had me stumped.

The correct answer is:
"My father thinks you've lost your ever lovin' mind."

Engineer here… not a guess on that.

quote:

Originally posted by scratchy:
The correct answer is " cake trays are racist/sexist/whateverist"

Class?

G.

A big gap between lines is 10, a small gap is 1.

The bottom right diagram is 20 wide and 17 tall, the area is the answer.

It’s just a specific shorthand way of drawing the obvious geometric interpretation.

Another engineer here. I agree with tatortodd, one shouldn't need a model for this. However, since education is pushing these things these days:

For a model, they would want something that is easily represented and is a whole number (like one model unit represents 100 cars or a 1,000 soldiers or maybe 1 million AR-15s). In this case, one of the model rectangles represents so many boxes of cake trays.

The boxes are the same size with each one representing X.

The 7 small (white) lines below represent the equivalent of 70% of a box (or 10% per line).

Similarly, the single line at the bottom of G represents the equivalent of 10% of a box. Solve for X for each model:

F: 4X + (2)(0.7)X = 17
X = 3.1481 Boxes
Not a logical model.

G: 4X + (2)(0.7)X + (2)(0.1)X + (1)(0.1)(0.7)X = 17
X = 2.9982 Boxes
Again, not a logical model

H: 3X + (3)(0.7)X = 17
X = 3.33333 Boxes
Once again, stupid model

I?: 2X + (2)(0.7)X = 17
X = 5 Boxes
An even number and the most logical choice as a "model" of the four choices presented.
Check: 2(5) + (2)(0.7)(5) = 17 √

EDIT: maladat posted while I was typing. His answer is better, incorporating the trays too, which I took as a given, and doesn't require the 4th graders to do algebra.

Can you say "common core"?

Fucking stupid. So glad I'm homeschooling and teaching my son actual math that's been used for centuries and still works today.

Tony.

I have an elementary school kid nearby so I was able to come up with this: Area models.

here's one that's solved.



in the OP's case, it's 10 , 10 from left to right (breaking down the 20), and then 10 , 7 from top to bottom (breaking down the 17).

So the kid breaks it down to 10*10 + 10*7 + 10*10 + 10*7 = 100 + 70 + 100 + 70 = 340

Maladat indeed has the correct answer.

It's no wonder we are ranked near the bottom worldwide in education when this kind of garbage is being taught.

It’s absolutely a stupid way to actually do math on paper.

That’s not the point.

Most people that do much math in their heads do multiplication in a way that is conceptually the same as those area models, and they are trying to teach kids to do that kind of mental math.

No idea how effectively it actually teaches that skill, but the goal makes sense.

Just because you don't immediately understand it doesn't mean it's a bad way to teach.

Everybody uses mnemonics to learn. Common core is a device... it teaches concepts that most smart people learned on their own even when it wasn't being taught to them. All it is, is breaking down large numbers into smaller sets of numbers that can be easily computed.

If a teacher explained it to you for 10 seconds you'd understand it. Is it always necessary? No. Because you already learned to do that problem by multiplying 7x2 and then adding it to 10x2. But this type of process can also work with much larger numbers that you can't simply do.

quote:

Originally posted by parabellum:

quote:

Originally posted by scratchy:
The correct answer is " cake trays are racist/sexist/whateverist"

Class?

Not intended to be political. I'll kill it, I was using snark, I failed.

quote:

Originally posted by scratchy:
Not intended to be political.

That's like mentioning a Chevy small block 350 and saying you didn't intend to speak about internal combustion engines.

H. It’s the only one with at least 20 trays.

And if that’s not right my guess is someone forgot to draw enough lines.

What's so hard about that? Two- (or more) place multiplication is grade-school stuff. Why does it need to be "modeled?" And if the illustrations are meant to represent cake trays …



… what kind of cake are you supposed to bake in those?

quote:

Originally posted by maladat:
Most people that do much math in their heads do multiplication in a way that is conceptually the same as those area models, and they are trying to teach kids to do that kind of mental math.

My 9th grade Algebra teacher spent the first 2 weeks of class teaching us how to do math in our heads and it was all done verbally. I can still do it well and I have no idea how to solve the OP's question offhand. I imagine I could work it out if I was willing to put time into it but I'm not.

My brain hurts.
When do we get to eat the cakes?

But, are they 'ghey cakes'?