LMD Async Tutoring

Time spent ~14mins

  • no teabags but everything else

    • OK: outcome = cup of tea
  • no milk but everything else

    • OK: outcome = cup of tea
  • no clean cup but everything else

    • asks if there is a clean cup in the cupboard, and if no, then it says to clean a cup. It doesn’t say where to look for a clean cup if there isn’t one in the cupboard. It also doesn’t suggest where to find a cup to clean. So if ‘no’ I think the flow chart would stall without using creativity. Outcome = no cup of tea
  • no teabags and no milk

    • if you decide you don’t want to end the process when you get a no, then you’ll go to the store two separate times. You’ll check for tea bags, go to the store and get some, then check for milk, then go to the store and get some. That’s just inconvenient and inefficient. It wouldn’t stall the flowchart though and you would still finish it without creativity. No optimal though. Outcome = cup of tea
  • no milk and no clean cup

    • This has the same issue as the no clean cup. You have to use creativity to find a cup to clean, or to find an already clean cup elsewhere. Outcome = no cup of tea
  • no clean cup and no tea bags

    • Same issue about clean cup. Outcome = no cup of tea
  • power outage

    • doesn’t really handle it. The kettle switch may flick on when you set it to boil but you’ll be stuck at ‘has the kettle finished boiling?’ until the power comes back on. Outcome = no cup of tea.
  • no running water

    • wont get past first step. Outcome = no cup of tea
  • kettle is broken

    • you’ll be stuck at ‘waiting to boil’. Outcome = no cup of tea
  • there are no cups (e.g the last one broke)

    • kinda similar to the no clean cups problem. you’ll never find one unless you go to the store to get one. Outcome = no cup of tea.

Good job finding that issue.

Sending someone to the store twice is a bad instructions. I don’t know why you’re downplaying that.

Could you update the flowchart to improve it based on your findings?

I don’t know why you’re downplaying that.

Hmm. I’m not sure either.

Sure. Here is an improved flow chart. I’ve also made the question explicit about whether you’re willing to go to the shops right now in order to make a cup of tea.

It looks longer. Being long or complicated is a negative. Can you find some ways to simplify/shorten it?

Okay. I’ve got rid of some of the details. This one seems more useful and intuitive. ~10 mins.

Here’s mine. What do you think of it?

Yeah okay. It’s obviously much simpler. Mine does looks pedantic and over-complex in comparison. Your doesn’t handle problems in the process that mine can and yours doesn’t have any decisions.

I guess when I thought about the process certain problems came up that I thought I shouldn’t just assume would be solved by background knowledge. Kinda like writing an algorithm. So am I including too much detail?

Writing anything well depends on your audience or goal. That kind of context helps you make decisions about what to include or exclude.

As a general rule of thumb for life, do the simplest thing that you don’t see an error with.

OK try a flowchart for solving a linear equation.

I’m finding this quite hard to put into words such that it applies in general. My flowchart feels too simple. But I didn’t want to get stuck on this for long.

Screenshot 2024-05-30 at 12.16.50 PM

Try using it on an example problem.

example problem: 9x + 1 = 10

  1. combine terms that contain the variable

there is only one term that contains the variable. I suppose this step could be rewritten as ‘reduce to one the number of terms that contain the variable if there are more than one’.

  1. isolate the variable by moving terms to the other side of the equation by undoing their operations

Ok. subtract 1 from both sides then divide both sides by 9.

example problem: (9x + 1)/2 = 5x

  1. combine terms that contain the variable

hmm. I don’t think there is a way to do this in one step. You’d have to first simplify the left expression, or multiply the right expression by 2/2 so they have the same denominator.

I feel a bit stuck and it’s causing me some frustration/distress.

Try a few problems using these steps:

Subtract (from both sides of the equation) any left-side constants. (Do the most basic simplification as you go. If there’s a 4 on the left, and you subtract 4, remove it instead of having 4-4).

Subtract any right-side terms with the variable.

Multiply by any denominators on the left.

Combine terms on the left (using addition and subtraction).

There’s now one variable term and its on the left. Divide by its coefficient.

Simplify the right side.

The result is x = n/m (where x is your variable and n and m are integers)

I’ve numbered those steps to reference:

  1. Subtract (from both sides of the equation) any left-side constants. (Do the most basic simplification as you go. If there’s a 4 on the left, and you subtract 4, remove it instead of having 4-4).

  2. Subtract any right-side terms with the variable.

  3. Multiply by any denominators on the left.

  4. Combine terms on the left (using addition and subtraction).

  5. There’s now one variable term and its on the left. Divide by its coefficient.

  6. Simplify the right side.

The result is x = n/m (where x is your variable and n and m are integers)


Example problem: 3c + 6 = 18

Step 1: subtract 6:
3c = 12

Steps 2, 3 and 4: none:
3c = 12

Step 5: divide by 3:
c = 12/3

Step 6: simplify:
c = 4
OK.

Example problem: 8 + 2/z = 10

Step 1: subtract 8:
2/z = 2

Step 2: none:
2/z = 2

Step 3: multiply by z:
2 = 2z

Step 4: none:
2 = 2z

Step 5: There is no variable on the left side any longer since step 3.

Not OK? I think it’d work if it didn’t specify which side the variable was on in step 5 and which side to simplify in step 6?

That’s not a linear equation because of the term 2z^-1

Linear equations raise variables to the 0 and 1 powers only.

To see the issue visually with x^-1 terms, go to wolfram alpha and enter these:

graph y = 3x

graph y = 3/x

As an equation with non-linear features, your example is a special case where it could be converted to a linear equation. Other examples like that include x^(1/2)=3 or y^3=8.

Oh okay cool. I can see that they don’t make straight lines on the graph. I don’t fully understand why. In the case of x^-1 it seems to have something to do with dividing by zero.

I’ll do some more problems with linear equations with your steps.

Example 3: 2(3 − h) − 6 = −5h

Step 0: the expression 2(3-h) needs to be expanded first

Step 1: subtract -6, subtract 6:
-2h = -5h

Step 2: Subtract -5h:
3h = 0

Step 3: none
3h = 0

Step 4: none

Step 5: divide by 3
h = 0/3

Step 6: simplify
h = 0

OK if we assume that brackets be expanded?

Example 4: (x + 2)/2 + (x + 4)/3 = 4

Step 1: none
(x + 2)/2 + (x + 4)/3 = 4

Step 2: none
(x + 2)/2 + (x + 4)/3 = 4

Step 3: multiply by 2 and 3 (6)
3x + 6 + 2x + 8 = 24

Step 4: combine terms
5x + 14 = 24

Step 5: Hmm there are two terms on the left, not just one and the variable.

Unless I’m messing up the first step by not subtracting the constants 2/2 and 4/3? That’d look like:

Step 1: subtract 2/2 (1), subtract 4/3
x/2 + x/3 = 5/3

Step 2: none
x/2 + x/3 = 5/3

Step 3: Multiply by 3 and 2 (6)
3x + 2x = 30/3

Step 4: Combine terms on left
5x = 10

Step 5: Divide by 5
x = 10/5
x = 2

OK.

The steps assume you’re dealing with separate terms. You could add a step to split things up first.

Sure. Should I keep working on example problems like this?

What did you think of my adding fractions flow chart?

It’s a bit vague like add the numerators sounds like you just take them, add them, and get a number (which it’s unclear what to do with).

Do you understand the steps? Does that help you see how to make some reasonable steps?

Do you understand the steps?

Yeah I think so. Here’s my understanding of the steps you gave.

  1. Subtract (from both sides of the equation) any left-side constants. (Do the most basic simplification as you go. If there’s a 4 on the left, and you subtract 4, remove it instead of having 4-4).

Step 1 means the left of the equation only has variable terms

  1. Subtract any right-side terms with the variable.

Step 2 means we only have variable terms on the left of the equation

  1. Multiply by any denominators on the left.

Step 3 gets rid of denominators on the left so you can then combine multiple instances of variables

  1. Combine terms on the left (using addition and subtraction).

Step 4 leaves us with one variable term

  1. There’s now one variable term and its on the left. Divide by its coefficient.

Step 5 tell us what one unit of the variable is equal to i.e what the solution is

  1. Simplify the right side.

Step 6 gives us the solution in the simplest form

So I think basically all the steps are there. I would add that separating the terms step, so: