document.write( "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
\n" ); document.write( " Hours (h) Total Cost(w)
\n" ); document.write( " 2 $110
\n" ); document.write( " 4 $155
\n" ); document.write( " 6 $200
\n" ); document.write( "for 7 hours of swimming lessons, which club is less expensive and by how much?
\n" ); document.write( "A. Dolphin swimming club, by $2.50
\n" ); document.write( "B. Mermaid swimming club, by $2,50
\n" ); document.write( "C. Dolphin swimming club, by $7.50
\n" ); document.write( "D. Mermaid swimming club, by $7,50 \n" ); document.write( "

Algebra.Com's Answer #773151 by math_helper(2461) $\"\"$ $\"About$

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document.write( "For Mermaid, 7hrs costs:
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document.write( "For Dolphin, we need to figure out the formula they use:
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document.write( "ASSUMING it is of the form f(h) = c*h + k   (h in hours, k is a constant, say
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document.write( "a sign-up fee)\r
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document.write( "From the given cost info:
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document.write( "  f(2) = c*2 + k = 110
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document.write( "  f(4) = c*4 + k = 155
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document.write( " (we don't need f(6) for this, but it can be used to check the formula
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document.write( "  we're about to derive)\r
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document.write( "solve these last two equations (one way: subtract f(2) from f(4)):
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document.write( "        2c = 45 -->  c=22.5  --> (using f(2) for example): k=65\r
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document.write( "For Dolphin, we have f(h) = 22.5*h + 65
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document.write( "[ check using f(6):  22.5*6 + 65 = 135 + 65 = 200 ]\r
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document.write( "Dolphin costs $222.50 for 7hrs of lessons, while Mermaid costs $215.00 for 
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document.write( "7hrs of lessons, or $7.50 less than Dolphin.\r
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