Wakaba buys some granola bars at $0.50 each and energy drinks at $2 each for a group hike. She buys twice as many granola bars as energy drinks. If she spends $27 in total, how many granola bars and energy drinks does she buy?

9 energy drinks and 18 granola bars.

Step-by-step explanation:

Price per granola bar = $0.50

Price per energy drink = $2.

We can define G as the number of granola bars that she bought, and D as the number of drinks that she bought.

Then

"She buys twice as many granola bars as energy drinks."

G = 2*D

" If she spends $27 in total"

G*$0.50 + D*$2 = $27

So we have a system of equations:

G = 2*D

G*$0.50 + D*$2 = $27

The first step will be to replace the first equation into the second one, and solve it for D.

(2D)*$0.50 + D*$2 = $27

D*(2*$0.50) + D*$2 = $27

D*$1 + D*$2 = $27

D*$3 = $27

D = $27/$3 = 9.

So she bought 9 energy drinks, and we know that:

G = 2*D

G = 2*9 = 18

She bought 18 granola bars.