SOLUTION: A marine platoon went on a 20 mile hike that took 6 hours to complete. for the first 12 miles the platoon hiked at a constant speed. For the last 8 miles he increased his speed b

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Question 314312: A marine platoon went on a 20 mile hike that took 6 hours to complete. for the first 12 miles the platoon hiked at a constant speed. For the last 8 miles he increased his speed by 1 mph. find the speed for the last part of the hike.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Rate*Time=Distance
+R1%2AT1=D1+
R1%2AT1=12
.
.
.
R2%2AT2=8
R2=R1%2B1
%28R1%2B1%29%2AT2=8
.
.
.
You also know that
T1%2BT2=6
.
.
.
From above,
T1=+12%2FR1
T2+=+8%2F%28R1%2B1%29
Substitute,
T1%2BT2=6
+12%2FR1%2B8%2F%28R1%2B1%29=6
12%28R1%2B1%29%2B8R1=6R1%28R1%2B1%29
12R1%2B12%2B8R1=6R1%5E2%2B6R1
6R1%5E2-14R1-12=0
%286R1%2B4%29%28R1-3%29=0
Two solutions but only positive solution makes sense in this problem.
R1-3=0
R1=3
Then from above,
highlight_green%28R2=4%29