Question

Ben and greg go to the movies and purchase snacks. Ben purchases four cookies and two bottles of water for a total cost of 9.00. Greg purchases two cookies and two bottles of water for a total cost of 7.00. What is the total cost of a bottle of water?

Answer 1

Good style in solving such problems is to notice/(to observe) immediately from the condition that the difference

between two combinations is the cost of 2 cookies, and it is equal to $9 - $7 = $2. So 2 cookies cost $2.

Then subtracting $2 dollars for 2 cookies from the Greg purchase, you got the cost of two bottles - it is equal to $7 - $2 = $5.

Answer. A bottle of water costs $2.50.

Explanation: