Question 1208986
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Answer: <font color=red>tight end's own 45 yard line</font>


Explanation:


TE = tight end
DB = defensive back


Let's find the TE's speed
distance = rate*time
d = r*t
r = d/t
r = (100 yards)/(12 seconds)
r = (100/12) yards per second
r = (25/3) yards per second
r = 8.3333 yards per second approximately


DB's speed
r = d/t
r = (100 yards)/(10 seconds)
r = (100/10) yards per second
r = 10 yards per second


After x number of seconds, the TE travels a distance of (25/3)x yards.
Meanwhile the DB travels 10x yards.


The gap between the players is initially 5 yards.
Whatever distance the TE travels, the DB must travel that distance plus 5 extra yards to catch up.
For example, if the TE travels 10 yards, then the DB must travel 10+5 = 15 yards to catch up to the TE.


DB's travel distance = (TE's travel distance) + 5 yards
10x = (25/3)x+5
3*10x = 3*( (25/3)x+5 )
30x = 25x+15
30x-25x = 15
5x = 15
x = 15/5
x = 3


The DB catches the TE at exactly the x = 3 second timestamp.
The DB catches (and perhaps tackles) the TE exactly 3 seconds after the TE caught the ball. 


After 3 seconds elapse, the TE traveled (25/3)*x = (25/3)*3 = 25 yards.
The TE goes from the 20 yard line to the 20+25 = <font color=red>45 yard line</font>. 
The TE has <u>not</u> crossed the midway marker since 45 < 50.
Therefore the TE is still on his side of the field.


Meanwhile the DB runs 10*x = 10*3 = 30 yards
The DB goes from the 15 yard line to the 15+30 = <font color=red>45 yard line</font>
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