"Ky (K) has 3 times more books than Grant (G), and Grant (G) has 6 fewer books than Jamie (J). if the total number of books is 176, how many books does Jamie (J) have?"
Hi Jaya-
Let me try and explain it another way. The main thing you want to look for with these types of questions are relationships. Then, your aim should be to write out expressions that convey those relationships. For example, the first sentence gives us a relationship between K and G, specifically that K has three times more books than G:
K = 3G
Next, we see a relationship between between G and J, namely that G has six fewer books than J:
J - 6 = G
Now we have represented the relationships in equations. Next, we can set up a third equation with all three variables, which we pull from the final sentence. It states that all the books add up to 176:
K + G + J = 176
We will use the last equation to solve for J. The problem with this equation is that we have three variables, and we can't solve for three variables. If, however, we can get just one variable, then we can isolate algebraically.
So, can we make this into an equation with one variable? Yes, by using the relationships we established and then substituting. This is how you do it:
K = 3G
J - 6 = G
First, you should notice that both of these relationships contain G. That is your clue that G is the variable you should be using in the final equation. Therefore, you need to figure out how to represent J and K in terms of G. Here's what you do:
Take the following equation:
K + G + J = 176
and substitute 3G for K (based on K = 3G)
3G + G + J = 176
Now you have only two variables. The next step is to get rid of the J; now we need the other relationship, namely J - 6 = G. Isolating for J, we get J = G + 6. Now substitute:
3G + G + (G + 6) = 176
And now, solve for G:
5G + 6 = 176
5G = 170
G = 34
And one final substitution, plugging in 34 to the following equation:
J - 6 = G
J - 6 = 34
J = 40
Jamie has 40 books. Hope that helped!
Arthur D.
04/14/14