The average cost of 4 sandwiches is is 7.25. The average of 3 sandwiches is 5.45. What is the cost of the fourth sandwich

Question

the average cost of 4 sandwiches is is 7.25. The average of 3 sandwiches is 5.45. What is the cost of the fourth sandwich

Answer 1

The average cost of 3 sandwiches can be visualized by writing

 

a + b + c  = 5.45   where a, b, and c are sandwiches.

       3

 

cross multiply and you will get a + b + c = 16.35.

 

Now use the same method for the 4 sandwiches:

 

a + b + c + d  = 7.25

         4

 

cross multiply and you will get a + b + c + d = 29

 

Now substitute the 16.35 in for a + b + c

 

You now have 16.35 + d = 29

simplify and d = $12.65

Answer 2

If the average cost of 4 sandwiches is 7.25 then the total cost of 4 sandwiches = 4x7.25 = 29.00

The total cost of 3 sandwiches = 3x5.45 = 16.35

The cost of the 4th sandwich = 29.00 - 16.35 = 12.65