Originally Posted by

**Dr.Peterson**
Here's how I'd do it; I'm not familiar with using superscripts as you did, which seems very confusing; I'll use a bar to separate "trusted" digits (those that are considered reliable based on significant figures or places) from others.

You want to evaluate 0.5230/1.2941 - (73.152 - 2.35)/0.001 * 5.72. It is possible that 0.001 is meant to be thought of as an exact number, so I'll take it that way after first evaluating it as having one significant figure:

0.5230/1.2941 - (73.152 - 2.35)/0.001 * 5.72 =

0.4041|41 - (70.80|2)/0.001 * 5.72 =

0.4041|41 - 7|0802 * 5.72 =

0.4041|41 - 4|04987.44 =

-4|04987.03

Keeping only the one trusted digit, the answer would be -400000!

If we take 0.001 as exact, we have

0.5230/1.2941 - (73.152 - 2.35)/0.001 * 5.72 =

0.4041|41 - (70.80|2)/0.001 * 5.72 =

0.4041|41 - 7080|2 * 5.72 =

0.4041|41 - 404|987.44 =

-404|987.03

so the answer would be -405000.

Subtraction between two numbers that differ so greatly in size essentially means that the smaller number can be ignored. In the second version here, only the thousands and higher places in the larger number are "trusted", to us my terms, so all digits in the smaller number are "down in the noise" and have no effect on the result.

In your answers, you included unreliable digits.

I forgot, I, too, tried -400,000 on one try! To no avail! Seeing your breakdown, -405000 seems to make the most sense to me of any attempt. However, I tried -405000 just now and it was also incorrect. I'm starting to think the answer key has an issue... Eek! So frustrating. I like using | to differentiate from your significant figures, I think I will start to do that rather than the superscript.

I meet with this teacher tomorrow... I will update you both... Thank you for taking a whack at this problem with me, I do appreciate it. It's really making me scratch my head

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