The resistance R to the motion of a car is partly constant and partly proportional to the square of the speed V. When the speed is 30 kilometers per hour the resistance is 190 newtons and when the speed is 50 kilometers per hour. Find for what speed the resistance is 302.5newton
r = a + bv^2
so, using the given info,
a+900v = 190
a+2500v = ?
fill in the missing ?, solve for a and b, and then solve
a+bv^2 = 302