TBR: Tricky Math Terminiology?

[justadream]

TBR: Math Wording?

Are these statements equivalent:

1) X must be increased by a factor of 2/3

2) X must be decreased by a factor of 2/3



Let X = 100.

I interpret statement 1 to be: 100 * 2/3 = 66.7 (for example, increasing something by a factor of TWO means you double it)



I interpret statement 2 to be 100 / (2/3) = 150 (for example, decreasing something by a factor of TWO means you halve it)



TBR claims these statements are the same (TBR Physics Book II page 152 #4).

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[el_duderino]

These statements are not the same. Can you quote exactly what TBR says?

 

[el_duderino]

BTW, I disagree with your interpretation. I would say that A would be 167. It does say increased, and interpreting it your way doesn't seem what was intended even if it can be technically correct.

 

[justadream]

@jonnythan

What would be your interpretation of decreased?

The exact question (which is irrelevant but I'll post it anyways is):

"Suppose the original oil droplet were replaced with a positively charged one that had twice the charge and three times the mass of the original droplet. How would the magnitude of the electric field have to be changed in order for the drop to remain suspended?"

B. It must be increased by a factor of 2/3
C. It must be decreased by a factor of 2/3


The answer key says "At the very least on this question, you could have eliminated choices B and C, as they are the exact same answer"

 

[el_duderino]

I would interpret it as 100 - (2/3)(100) = 33

Anyway this is just one of ose dumb TBR/TPR/EK things. I hate those sources for questions because they're hack jobs. They're only useful for content review IMO because the character of the questions is just so different from AAMC and they're low quality.