<PRE><B>Question 166104</B>
total AVERAGE rate of speed for entire trip we will call r=22.5

r1=20---1st 80mi
r2=30---next 60mi
r3=unknown(this is what we are trying to find--- of final 40mi

(r1+r2+r3)/3=r

20+30+r3=3(22.5)
r3=67.5-50
r3=17.5kmph
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