document.write( "Question 894195: In deep sea diving, the pressure exerted by water plays a great role in designing underwater equipment. If at a depth of 10 feet there is a pressure of 21 lb/in (squared), and at a depth of 50 feet there is a pressure of 75 lb/in (squared), write an equation giving a relationship between depth and pressure. Use this relationship to predict pressure at a depth of 100 feet. I tried figuring the slope and then using the formula y = mx + b. It didn't work out to be the solution tht was in my book of y = 1.35x + 15.2. I can't figure how this equation was arrived at. \n" ); document.write( "
Algebra.Com's Answer #541866 by ankor@dixie-net.com(22740)\"\" \"About 
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In deep sea diving, the pressure exerted by water plays a great role in designing underwater equipment.
\n" ); document.write( " If at a depth of 10 feet there is a pressure of 21 lb/in (squared), and at a depth of 50 feet there is a pressure of 75 lb/in (squared), write an equation giving a relationship between depth and pressure.
\n" ); document.write( " Use this relationship to predict pressure at a depth of 100 feet.
\n" ); document.write( ":
\n" ); document.write( "I don't get that either, my calculations:
\n" ); document.write( ":
\n" ); document.write( "The slope formula; m = \"%28y2-y1%29%2F%28x2-x1%29\"
\n" ); document.write( "Assign the given values as follows:
\n" ); document.write( "x1=10; y1=21
\n" ); document.write( "x2=50; y2=75
\n" ); document.write( "Find the slope
\n" ); document.write( "m = \"%2875-21%29%2F%2850-10%29\" = \"54%2F40\" = \"27%2F20\" is the slope
\n" ); document.write( "now we have
\n" ); document.write( "\"27%2F20\"x + b = y
\n" ); document.write( "go to decimals
\n" ); document.write( "1.35x + b = y
\n" ); document.write( "Replace x with 10 and y with 21, find b
\n" ); document.write( "1.35(10) + b = 21
\n" ); document.write( "13.5 + b = 21
\n" ); document.write( "b = 21 - 13.5
\n" ); document.write( "b = 7.5
\n" ); document.write( "the equation
\n" ); document.write( "y = 1.35x + 7.5
\n" ); document.write( ":
\n" ); document.write( "Use this relationship to predict pressure at a depth of 100 feet.
\n" ); document.write( "y = 1.35(100) + 7.5
\n" ); document.write( "y = 135 + 7.5
\n" ); document.write( "y = 142.5 psi at 100 ft
\n" ); document.write( ":
\n" ); document.write( ":
\n" ); document.write( "I put this equation in my Ti83, looked at the table and it agreed with the given x/y values.
\n" ); document.write( "The equation they give does not do that. For x=10, it comes up with y=28.7!
\n" ); document.write( "Book is wrong!\r
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