GMAT Word Problems: If x and y are related by the equation…
Question
Next year, if Company Q produces x units of a certain product and sells y units of this product, its total profit, in dollars, from this product will be 10y - 4x. If x and y are related by the equation y = rx and if Company Q's average (arithmetic mean) profit per item produced next year must be at least $4.50, what is the least possible value of r?
- 0.65
- 0.70
- 0.75
- 0.80
- 0.85
Topics: word problems, linear equations, inequalities
Solution
Step 1
We translate "average profit per item produced next year must be at least 4.50" into an inequality comparing profit per item to 4.50.
(10y-4x)/x ≥ 4.50
Step 2
We substitute "y = rx" into the inequality to express everything in terms of r and x.
(10(rx)-4x)/x ≥ 4.50
Step 3
We simplify the numerator by factoring out x and then cancel x from numerator and denominator.
(x(10r-4))/x ≥ 4.50 10r - 4 ≥ 4.50
Step 4
We add 4 to both sides of the inequality to isolate the term with r.
10r ≥ 4.50 + 4
Step 5
We divide both sides by 10 to solve for r.
r ≥ (8.50)/10 = 0.85
Answer
0.85 (E)
