Stock Market Fractions

Date: 04/05/2002 at 11:41:16
From: Jennifer
Subject: Fractions

Stock closed on Friday at a price of 42 5/8. On Monday stock closed 
at 39 7/8. How much did the market value of stock drop on Monday?

Date: 04/05/2002 at 13:23:03
From: Doctor Ian
Subject: Re: Fractions

Hi Jennifer,

Once you strip away the irrelevant details, you're left with the 
problem

  42 5/8 - 39 7/8 = ?

There are at least a couple of ways you could go about answering this.  
One would be to recognize that 1/8 is the same as 0.125, so the 
problem is equivalent to 

  45.625 - 39.875 = ?

Another way to deal with it would be to figure out what you'd need to 
add to 39 7/8 to get up to 42 5/8.  I would do that in two steps:

  1. How much would you have to add to get from 39 7/8 to 40?

  2. How much would you have to add to 40 to get to 42 5/8?

Add the results of steps 1 and 2 together, and you have your answer.

Okay, there is a third way to do it, too, which is probably what 
you're 'supposed' to do: Convert 42 5/8 to 41 13/8 (do you see why 
they're the same?), to make the subtraction easier:

  42 5/8 - 39 7/8 = 41 13/8 - 39 7/8 = ?
  
This is similar to what you do when you perform a carry in 
subtraction. 

I hope this helps. Write back if you'd like to talk more about this, 
or anything else.

- Doctor Ian, The Math Forum
  http://mathforum.org/dr.math/