   SEARCH HOME Math Central Quandaries & Queries  Question from sandhiya, a student: one group of people purchased 10 hotdogs and 5 soft drinks at a cost of $12.50.asecond group bought 7 hotdogs and 4 soft drinks at a cost of$9.00 find the cost of a single hot and a single soft drink.(using the row echelon form to solve) Hi Sandhiya,

I can help get you started.

First I am going to write the cost on cents rather than dollars so that I can work with integers. Let h be the cost of a hotdog in cents and s be the cost of a soft drink in cents. Then for the first group

10 h + 5 s = 1250

and for the second group

7 h + 4 s = 900.

The augmented matrix for this system of linear equations is then The first thing I notice is that the first row has a common factor of 5 so multiply the first row by 1/5 Multiply the first row by -3 add add it to the second row Can you complete the problem now?

Penny     Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.