SOLUTION: Andrea is shopping at a bulk store. She needs to buy flour, sudar and salt. She needs twices as much flour as sugar and tic as musch sugar as salt. She plans to buy a total of 10.5

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Question 27063: Andrea is shopping at a bulk store. She needs to buy flour, sudar and salt. She needs twices as much flour as sugar and tic as musch sugar as salt. She plans to buy a total of 10.5 pounds of flour, sugar and salt combined. Flour is $1.20 a pound, sugar is $2.30 a pound, and salt is $.68 a pound. How much of each item will she need to buy and how much will it cost?
Answer by mbarugel(146) (Show Source):
You can put this solution on YOUR website!
We must "translate" all this data into equations. Let's call A to the amount of flour, B to the amount of sugar, and C to the amount of salt. Now,
She needs twices as much flour as sugar:
and twice as much sugar as salt:
She plans to buy a total of 10.5 pounds of flour, sugar and salt combined:
Given these three equations, we can solve the system. First substitute the second one into the first one:

Then we substitute this result into the third one:

Finally, we subsitute again the second one into the one we've just found:

So shw will buy 1.5 pounds of salt. Since she will buy twice as much sugas as salt, she will buy 3 pounds of sugar. And clearly, she will be buy 6 pounds of flour.
Using the given prices, she will spend:
6*1.20 + 3*2.30+ 1.5*0.68 = 15.12
she'll spend $15.12