The speeds of the planes are 260 miles/hr and 290 miles/hr respectively.
We know that the velocity or speed is the ratio of total distance to time taken.
Let speed of another plane be x miles per hour.
Now, one plane can travel 30 miles per hour more than previous one.
So the speed of this second plane = x+30 miles per hour.
Time taken by first plane to cover 390 miles = 390/x
Time taken by second plane to cover 435 miles = 435/(x+30)
According to question the time taken is equal. So,
390/x = 435/(x+30)
26/x = 29/(x+30)
26x+780 = 29x
29x-26x = 780
3x = 780
x = 780/3
x = 260
The speed of first plane = 260 miles/hour
The speed of second plane = 260+30 = 290 miles/ hour
Hence the speeds of the planes are 260 miles/hr and 290 miles/hr respectively.
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