Question 481055
120/p=120/(p+10)+36/60
120/p=120/(p+10)+.6
1200/p=1200/(p+10)+6
1200(p+10)=1200p+6p2+60p
1200p+12000=1200p+6p2+60p
6p2+60p-12000=0
p2+10p-2000=0
(p+50)(p-40)=0
p=40 or -50
Throwing out the negative answer, we get the motorist's actual average speed to be 40 mph..