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Question 1151412: Mermaid Swimming Club uses the equation w=25h+40 to calculate the total cost, w,of h hours of swim lessons. Use the table below by Dolphin swimming club to calculate the cost of swimming lessons for its customers
Hours (h) Total Cost(w)
2 $110
4 $155
6 $200
for 7 hours of swimming lessons, which club is less expensive and by how much?
A. Dolphin swimming club, by $2.50
B. Mermaid swimming club, by $2,50
C. Dolphin swimming club, by $7.50
D. Mermaid swimming club, by $7,50
Answer by math_helper(2461)   (Show Source):
You can put this solution on YOUR website!
Solution, with assumptions...
For Mermaid, 7hrs costs:
For Dolphin, we need to figure out the formula they use:
ASSUMING it is of the form f(h) = c*h + k (h in hours, k is a constant, say
a sign-up fee)
From the given cost info:
f(2) = c*2 + k = 110
f(4) = c*4 + k = 155
(we don't need f(6) for this, but it can be used to check the formula
we're about to derive)
solve these last two equations (one way: subtract f(2) from f(4)):
2c = 45 --> c=22.5 --> (using f(2) for example): k=65
For Dolphin, we have f(h) = 22.5*h + 65
[ check using f(6): 22.5*6 + 65 = 135 + 65 = 200 ]
Dolphin costs $222.50 for 7hrs of lessons, while Mermaid costs $215.00 for
7hrs of lessons, or $7.50 less than Dolphin.
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