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Finding the Weight of an Egg

Date: 2/9/96 at 15:27:25
From: Anonymous
Subject: word problem

If an egg weighs 20 grams and half an egg, what does an egg 
and a half weigh?

Date: 2/14/96 at 10:32:22
From: Doctor Byron
Subject: Re: word problem

Here are two ways to tackle your egg problem:

First, we notice that the first sentence says that:  "An egg weighs 20 
grams plus half an egg."  Clearly, if the weight of the egg is made up 
only of two parts, one which is half the egg, the remaining weight must 
also be half the weight of the egg.  This remaining weight is 20 grams.  
Therefore, half the weight of the egg is 20 grams.  Multiplying by 3 to 
get the weight of an egg and a half, we get 60 grams.

Now let's try to re-work your problem into a simple algebraic 
expression.  I'll start by calling 'e' the weight of a full egg.  The 
first part says:

'An egg weighs 20 grams and half and egg'.  This is equivalent to:

e = 20 + e/2

By subtracting e/2 from both sides we have:

e/2 = 20

Now by multiplying both sides by 2, we see that 

e = 40.

So the egg weighs 40 grams.  Therefore an egg and a half would weigh
60 grams.

-Doctor Byron,  The Math Forum

Associated Topics:
Middle School Word Problems

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