document.write( "Question 198257: respected sir,\r
\n" ); document.write( "\n" ); document.write( "1] A and B ran a race of 480 m. In the first heat, A gives B a head start of 48 m and beats him by 1/10 th of a minute. In the second heat, A gives B a head start of 144 m and is beaten by 1/30 th of a minute. What is B’s speed in m/s?\r
\n" ); document.write( "\n" ); document.write( "plz solve my doubt..\r
\n" ); document.write( "\n" ); document.write( "thank u.
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Algebra.Com's Answer #148746 by josmiceli(19441)\"\" \"About 
You can put this solution on YOUR website!
What the problem doesn't say, and must be assumed is that
\n" ); document.write( "A and B each travel at constant speeds. I can then write a
\n" ); document.write( "constant speed equation for each and for each race:\r
\n" ); document.write( "\n" ); document.write( "\"d%5Ba%5D+=+r%5Ba%5D%2At%5Ba%5D\"
\n" ); document.write( "\"d%5Bb%5D+=+r%5Bb%5D%2At%5Bb%5D\"
\n" ); document.write( "If a have a stopwatch, I want to start timing the race when
\n" ); document.write( "both runners are in motion, so I'll start it when A begins
\n" ); document.write( "running for each race.
\n" ); document.write( "1st race:
\n" ); document.write( "\"d%5Ba%5D+=+480\"
\n" ); document.write( "\"d%5Bb%5D+=+480+-+48\"
\n" ); document.write( "\"d%5Bb%5D+=+432\"
\n" ); document.write( "\"t%5Ba%5D+=+t%5Bb%5D+-+1%2F10\"
\n" ); document.write( "\"t%5Bb%5D+=+t%5Ba%5D+%2B+1%2F10\"
\n" ); document.write( "-------------------
\n" ); document.write( "\"480+=+r%5Ba%5D%2At%5Ba%5D\" (same for both races)
\n" ); document.write( "\"432+=+r%5Bb%5D%2A%28t%5Ba%5D+%2B+1%2F10%29\"
\n" ); document.write( "--------------------
\n" ); document.write( "2nd race:
\n" ); document.write( "\"d%5Ba%5D+=+480\"
\n" ); document.write( "\"d%5Bb%5D+=+480+-+144\"
\n" ); document.write( "\"d%5Bb%5D+=+336\"
\n" ); document.write( "\"t%5Bb%5D+=+t%5Ba%5D+-+1%2F30\"
\n" ); document.write( "----------------------
\n" ); document.write( "\"480+=+r%5Ba%5D%2At%5Ba%5D\"
\n" ); document.write( "\"336+=+r%5Bb%5D%2A%28t%5Ba%5D+-+1%2F30%29\"
\n" ); document.write( "----------------------
\n" ); document.write( "r[a] and r[b] are the same in both races.
\n" ); document.write( "Also, t[a] is the same in both races, but
\n" ); document.write( "t[b] is not the same .
\n" ); document.write( "In race 1:
\n" ); document.write( "\"432+=+r%5Bb%5D%2A%28t%5Ba%5D+%2B+1%2F10%29\"
\n" ); document.write( "\"r%5Bb%5D+=+432%2F%28t%5Ba%5D+%2B+1%2F10%29\"
\n" ); document.write( "I can plug this into the equation from race 2
\n" ); document.write( "\"336+=+r%5Bb%5D%2A%28t%5Ba%5D+-+1%2F30%29\"
\n" ); document.write( "\"336+=+%28432%2F%28t%5Ba%5D+%2B+1%2F10%29%29%2A%28t%5Ba%5D+-+1%2F30%29\"
\n" ); document.write( "Multiply both sides by \"t%5Ba%5D+%2B+1%2F10\"
\n" ); document.write( "\"336%2A%28t%5Ba%5D+%2B+1%2F10%29+=+432%2A%28t%5Ba%5D+-+1%2F30%29\"
\n" ); document.write( "\"336t%5Ba%5D+%2B+33.6+=+432t%5Ba%5D+-+14.4\"
\n" ); document.write( "\"96t%5Ba%5D+=+48\"
\n" ); document.write( "\"t%5Ba%5D+=+.5\"
\n" ); document.write( "The time for A is 30 sec
\n" ); document.write( "\"480+=+r%5Ba%5D%2At%5Ba%5D\"
\n" ); document.write( "\"480+=+r%5Ba%5D%2A.5\"
\n" ); document.write( "\"r%5Ba%5D+=+960\" m/min
\n" ); document.write( "\"432+=+r%5Bb%5D%2A%28t%5Ba%5D+%2B+1%2F10%29\" (1st race)
\n" ); document.write( "\"432+=+r%5Bb%5D%2A%28.5+%2B+.1%29\"
\n" ); document.write( "\"r%5Bb%5D+=+432%2F.6\"
\n" ); document.write( "\"r%5Bb%5D+=+720\" m/min
\n" ); document.write( "\"720\" m/min * \"1%2F60\" min/sec = \"12\" m/sec
\n" ); document.write( "B's speed is 12 m/sec
\n" ); document.write( "---------------------
\n" ); document.write( "check answer:
\n" ); document.write( "\"336+=+r%5Bb%5D%2A%28t%5Ba%5D+-+1%2F30%29\" (2nd race)
\n" ); document.write( "\"336+=+r%5Bb%5D%2A%2815%2F30+-+1%2F30%29\"
\n" ); document.write( "\"336+=+r%5Bb%5D%2A%2814%2F30%29\"
\n" ); document.write( "\"r%5Bb%5D+=+10080%2F14\"
\n" ); document.write( "\"r%5Bb%5D+=+720\" m/min
\n" ); document.write( "\"720\" m/min = \"12\" m/sec
\n" ); document.write( "OK
\n" ); document.write( "To see the whole thing, I could plot time (sec) on
\n" ); document.write( "the x-axis and distance (m) on the y-axis for
\n" ); document.write( "I want to look at \"d+=+480\"m
\n" ); document.write( "\"d+=+16t\" (both races)
\n" ); document.write( "\"d+-+48+=+12t\" B, 1st race
\n" ); document.write( "\"d+-+144+=+12t\" B, 2nd race
\n" ); document.write( " \"+graph%28+700%2C+400%2C+-10%2C+60%2C+-50%2C+700%2C+16x%2C12x+%2B+48%2C12x+%2B+144%29+\"
\n" ); document.write( "The line starting at the origin is A's plot.
\n" ); document.write( "Where \"d+=+480\" shows the times to get to finish
\n" ); document.write( " \"+graph%28+700%2C+400%2C+-10%2C+60%2C+300%2C+700%2C+16x%2C12x+%2B+48%2C12x+%2B+144%29+\"
\n" ); document.write( "This is a blow-up
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