An airplane flew 3.5 hours with a 40 mph head wind. The return trip with a tail wind of the same speed took 2.5 hours. How do you find the speed of the plane in still air?

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Answer 1 · 2017-03-15T17:51:59

#"air velocity "=" "240 mph#

Let the velocity of the plane relative to still air be #v#

Let the ground distance be #d#

Distance = velocity #xx# time

Up wind the velocity #ul("relative to the ground")# will be #v-40#
Down wind the velocity #ul("relative to the ground")# will be #v+40#

#(v-40)xx3.5 = d= (v+40)xx2.5#

#3.5v-140=2.5v+100#

#3.5v-2.5v=100+140#

#v=240 mph#