Posted by Taylor on Monday, January 24, 2011 at 9:24pm.
RT = D
T = time for Tom
T - 6.5 = time for John (-4s + -2.5s)
R = rate for Tom
R + 5 = rate for John
D = 650
RT = D
RT = 650
(R + 5)(T - 6.5) = 650
Solve these equations simultaneously.
Expand (R + 5)(T - 6.5) = 650
Then substitute, RT = 650 for RT in the expansion.
Why did you add -4s + -2.5s ?
John sets off 4 seconds after Tom does, and finishes the lap 2.5 seconds sooner than Tom does.
So, John's total time will be 6.5 sec less than Tom's time.
Do you understand?
Also, If you solved correctly, R = 20 and T = 32.5.
Remember, the problem wants each racers' speed and time.
So use the below to calculate that after you solve the equations for T and R.
T = time for Tom
R = rate for Tom
T - 6.5 = time for John
R + 5 = rate for John
Okay, I understand now, thanks!
You're welcome!
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