ziyuenlau wrote:The function of the relationship between the cost (c) and the revenue (x) is the equal to c(cost)=bx+a. If the revenue is increased by $1,000, by how many dollars did the cost increase?
1) a=10
2) b=20
OA=B
Given c = bx + a, we find the Cost (c) is proportional to Revenue (x). Since 'a' is constant, the value of 'c' would not differ for x = $100 or for x = $1000. Thus, knowing the value of 'b' is sufficient.
The correct answer:
B
Let's compute for the sake of understanding...
C (@x) = 20x + a ---(1)
Thus,
C (@x+1000) = 20*(x+1000) + a ---(2)
Eqn (2) - Eqn (1)
Thus, C (@x+1000) - C (@x) = 20*(x+1000) + a - 20x - a = 20000
Increase in Cost = $20,000
Hope this helps!
Relevant book:
Manhattan Review GMAT Data Sufficiency Guide
Jay
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