If the cost of a video game, C, is C=RT^2−3T+8, what is the cost, in dollars, if R=8 and T=−2?

Question

(1 mark for substituting given values correctly, 1 mark for simplifying, 1 mark for correct cost value, 1 mark for 'therefore' statement with correct units)

Answer 1

Jahroy,

You're given a formula (C=RT^2−3T+8

) with three variables or unknowns (C, R, and T). If someone gives you any two of those, then they are known and you can solve for the third, variable, which is still unknown.

C = RT² − 3T + 8

R = 8

T = –2

Substitute the above values for R and T in the formula.

C = RT² − 3T + 8

C = (8) (–2)² – 3(–2) + 8 (the parentheses were simply added for clarification)

Now evaluate or simplify this.

C = (8)(4) – (–6) + 8

Continue to simplify.

C = (8)(4) – (–6) + 8

C = 32 + 6 + 8

C = 38 + 8

C = 46

The word problem did not ask for the value of C; it asked for the cost of the video game. You should answer a word problem in a complete sentence. Thus, your answer is: The cost of a video game is $46.