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by jscpba » Wed Jan 12, 2011 10:34 pm
Store sells all maps at one price and all books at another price. Monday the store sol 12 maps and 10 books totally $38. Tuesday the store sold 20 maps and 15 books for $60. How much less does a map sell for than a book?

a $.25
b $.50
c $.75
d $1.00
e $1.25

I realize that the two equations are 12m+10b=38 and 20m+15b=60

What I don't realize is why I am supposed to multiply the first equation by -3/2?
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by ankur.agrawal » Wed Jan 12, 2011 11:01 pm
jscpba wrote:Store sells all maps at one price and all books at another price. Monday the store sol 12 maps and 10 books totally $38. Tuesday the store sold 20 maps and 15 books for $60. How much less does a map sell for than a book?

a $.25
b $.50
c $.75
d $1.00
e $1.25

I realize that the two equations are 12m+10b=38 and 20m+15b=60

What I don't realize is why I am supposed to multiply the first equation by -3/2?
Becoz dat wud convert the 1st Eqn to : -18m-15b = -51 . 2nd equation is 20m+ 15b=60. Now u can easily solve for m & b.

Better is multiply 1st Eqn by 3 & 2nd Eqn by 2. More intuitive.

Hope it helps
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