Question 112275
THE BEST PLACE TO START WHEN SOLVING WORD PROBLEMS IS:
FIRST, FIGURE OUT WHAT THE PROBLEM IS ASKING YOU TO DETERMINE (IN THIS CASE IT'S THE SELLING PRICE PER KILO OF A GRATED CHEESE MIXTURE)AND,THEN,ASSIGN AN UNKNOWN (OR UNKNOWNS)TO REPRESENT WHAT YOU ARE TRYING TO DETERMINE.
NEXT, TRY TO FIGURE OUT HOW TO SET UP THE EQUATION THAT YOU WILL SOLVE IN ORDER TO DETERMINE THE UNKNOWN(S). IN THIS CASE IT WAS EASY BECAUSE WE KNOW THAT THE THE TOTAL PRICE BEFORE THE MIXTURE HAS TO EQUAL THE TOTAL PRICE AFTER THE MIXTURE.
FINALLY, SOLVE THE EQUATION THAT YOU HAVE SET UP AND CHECK TO SEE IF THE CONDITIONS OF THE PROBLEM ARE MET.

LAY OUT THE PROBLEM IN AN ORDERLY FASHION
Let x=selling price per kilo of the final grated cheese mixture

Now we know that the total cost of the final mixture ((6kg+15kg)*x) has to equal the total cost of the grated cheese before the mixture takes place (6 kg*$10.50+15 kg*$7.00).  So our equation to solve is:

21x=6*$10.50+15*$7.00

21x=$63+$105  

21x=$168  divide both sides by 21

x=$8 per kilo

CK

$8*21 kg=$10.50*6 kg+$7.00*15 kg

$168 =$63+$105
$168=$168


Hope this helps----ptaylor