document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=585316>Question 585316</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi:) HW question. I have done the first 3 parts successfully, I believe. It's the whole cricket chirping thing. My question is for D). How to find the temp in F when chirping is 40 chirps in 30 seconds (1/2 minute). The first 3 parts are as follows: 68F, 24 chirps/minute. 40F, 86 chirps/minute. A) Express the #chirps as a linear function of the F temp (x). So I wrote, y= -2.214x + 174.552. B) Interpret slope in a sentence. I wrote, for every 1 degree F increase of temp, the # chirps decreases by 2.214 chirps. C) If temp is 60F, how many chirps/minute? I wrote 41.712. (Teacher wants 3 decimal places.) D)If there are 40 chirps in 1/2 minute, what is temp? I have spent soo much time trying to figure this D part but am stuck. I appreciate any help. Thank you. </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #373281 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=373281\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> when temp is 68, number of chirps per minute is 24 chirps per minute.<BR>\n" );
document.write( "when temp is 40, number of chirps per minute is 86 chirps per minute.<BR>\n" );
document.write( "x = degrees Fahrenheit.<BR>\n" );
document.write( "y = number of chirps per minute.<BR>\n" );
document.write( "PART A:<BR>\n" );
document.write( "express as linear equation.<BR>\n" );
document.write( "x1,y1 = 68,24<BR>\n" );
document.write( "x2,y2 = 40,86<BR>\n" );
document.write( "slope of line is (24-86) / (68-40) = -62 / 28 = -2.21428571<BR>\n" );
document.write( "slope intercept form of equation is:<BR>\n" );
document.write( "y = mx + b<BR>\n" );
document.write( "m is slope<BR>\n" );
document.write( "b is y intercept.<BR>\n" );
document.write( "replace m with -2.21428571 to get:<BR>\n" );
document.write( "y = -2.21428571*x + b<BR>\n" );
document.write( "replace y with 24 and x with 68 to get:<BR>\n" );
document.write( "24 = -2.21428571*68 + b<BR>\n" );
document.write( "solve for b to get:<BR>\n" );
document.write( "b = 174.5714283<BR>\n" );
document.write( "so far so good.<BR>\n" );
document.write( "a little off probably due to rounding (you did i didn't).<BR>\n" );
document.write( "PART B:<BR>\n" );
document.write( "your explanation is good.<BR>\n" );
document.write( "you lose 2.214 chirps per minute for every increase of 1 degree.<BR>\n" );
document.write( "PART C:<BR>\n" );
document.write( "when temp is 60 degrees, number of chirps per minute is equal to:<BR>\n" );
document.write( "-2.21428571*60 + 174.5714283 which is equal to 41.71428568.<BR>\n" );
document.write( "you're still good.<BR>\n" );
document.write( "PART D:<BR>\n" );
document.write( "If there are 40 chirps in 1/2 minute, what is temp?<BR>\n" );
document.write( "40 chirps in 1/2 minute is equivalent to 80 chirps in 1 minute.<BR>\n" );
document.write( "replace y with 80 in your equation and solve for x.<BR>\n" );
document.write( "your equation is:<BR>\n" );
document.write( "y = -2.21428571*x + 174.5714283<BR>\n" );
document.write( "replacing y with 80 gets you:<BR>\n" );
document.write( "80 = -2.21428571*x + 174.5714283<BR>\n" );
document.write( "subtract 174.5714283 from both sides of this equation to get:<BR>\n" );
document.write( "-94.57142828 = -2.21428571*x<BR>\n" );
document.write( "divide both sides of this equation by to get -2.21428571 to get x = 42.70967737 degrees.<BR>\n" );
document.write( "that's your answer.<BR>\n" );
document.write( "x = 42.70967737 which is the number of degrees fahrenheit that will generate 80 chirps per minute based on the equation.<BR>\n" );
document.write( "a graph of your equation of:<BR>\n" );
document.write( "a horizontal line at y = 80 has been drawn to intersect with a vertical line at x = 42.70967737 to show you where that point would be on the line of the equation.<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=graph%28600%2C600%2C-20%2C100%2C-20%2C200%2C-2.21428571%2Ax%2B174.5714283%2C80%2C400%2A%28x-42.70967737%29%29 ALIGN=MIDDLE   DISABLED_style= \"max-width:90%; height:auto;\" >\r<BR>\n" );
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document.write( " </SPAN>\n" );
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