15 August 2006

RightStart Geometry

The continuing saga of our adventures using RightStart Geometry and RightStart B. I have a 10yo and a 6yo who have average math ability.The 10yo has done Miquon, Singapore, RightStart Transitions, Level D and Level E; RightStart has saved her from a life a math phobia.

On Tuesdays I upload an update of what we did in math for the week.

RightStart Geometry:

Lesson 35 Converting Inches to Centimeters. I noticed a sidebar on this lesson that gave a mnemonic for the conversion: 1 inch = 2.54 cm is like $1 is 25(quarter) times 4. Hmmm, how clever. I memorized the conversion through brute memorization of using it so often, although I typically use 1 inch equals 2.5 cm when I’m in a hurry (a 4 inch by 4 inch swatch of knitting is the same as a 10 cm by 10 cm swatch, as knitters all over the US are well aware).

After Kid1 completes the lesson I ask if if she remembers the conversion factor. She says, “yeah, it’s 2.75 ... wait, that’s not right ... .” “Wrong number of quarters, I think.” “Yeah, I knew it was something to do with quarters.” I start to pontificate that it’s better to remember it in regards to knitting swatches, and am about to start in on converting seam allowances in home sewing, but she wanders off.

Overall, though, I think maybe the the straight forward memorization is better than the mnemonic. I think she’ll eventually remember it the way I do, through extensive use in sewing and knitting.

Lesson 36 Name that Figure. Fun little game of naming figures which introduces the practice of using letters to indicate vertices. Also has a clever way to remember how to spell Isosceles. Sometimes she simply can’t remember the names of these figures. I worry about that -- does this mean she doesn’t “get” geometry?

Lesson 37 Finding the Areas of More Triangles. The worksheet includes the Guyana Flag problem, which was also in Level E. For some reason we did not do that lesson in Level E, so Kid1 is stymied ... she is trying to measure the sides of the flag in millimeters, and figure out the conversion ratio to give her the measurements given on the worksheet. I point out that she has everything she needs to know without measuring -- the worksheet says the left side is 26cm, the upper edge is 33.8cm, and point E is the center of the flag; we should assume it’s a perfect rectangle.

“Oh!” she exclaims, “that means these 4 triangles have the same area!” Ummmm, does it? I’m not sure off the top of my head, so I cover my confusion by pointing out that we know half the side will be 13cm, etc. etc. so we can find the area of all these other triangles.

As she gets to work I pull out Level E and flip to the lesson. I notice a sidebar: “A gifted child might notice that the triangles each take up 1/4 the rectangle.”

“Hey, guess what! According to this you’re gifted!” Ho ho ho, we laugh. After all, Kid1 is thoroughly convinced she stinks at math ... at least she was until we got involved in RightStart. I guess my worries yesterday were a bit unfounded -- some stuff she’s really good at, some stuff she still needs to work on.

Lesson 39 Area of Trapezoids. First problem; we also didn’t do the Level E lesson on distributive property. Although the geometry book explains it well, I give her a quick rundown (“Pretend I have the invecta balance here and I’m hanging those weights on it....”) and assure her that kids who never saw Level E or any RightStart whatsoever can figure this out. She runs into problems with the worksheet. The book has shown one reason the area of a trapezoid can be expressed as w1 plus w2 times h over 2. She is supposed to discover and explain another way of understanding it: 2 identical trapezoids, rotated and shoved together, make a parallelogram; if you find the area of the parallelogram and divide it in 2, you have the same formula.

She looks frustrated by the concept -- what the heck does the book want? What are they getting at? I say something to the effect, “they just want you to say that since you have 2 identical trapezoids of course you can divide the answer in half. I think maybe it’s so obvious you don’t understand why you have to say it. It’s that ‘gifted child’ thing from yesterday, you know.” She giggles, the mood lightens, and she continues with the lesson.

Lesson 39 Area of Hexagons. She starts off commenting, “you know what? There was another worksheet in the last lesson I didn’t do.” “Are you going to do it now?” “No, I don’t think so.” Thank goodness, because this lesson took at least 1.5 hours as it was. Of course, within that time we ran into a whoppin’ huge fight on the definition of a trapezoid -- for some reason she had concluded that an isosceles trapezoid wasn’t actually a trapezoid, possibly because all the trapezoids she’s been working with are non-isosceles. Thankfully, I found one pictured in lesson 36 (under the lesson on how to spell “isosceles”). Also, she’s quite peeved that 1.2 times 1.4 doesn’t equal something bigger than 1.68 ... pesky decimals.

The final problem involves measuring stars that she had drawn in earlier lessons. I’m glad I’m on hand to demonstrate that you round off the measurements quite a bit to get the ratios needed.

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