Two airplanes leave Chicago's Midway airport at the same time, traveling in opposite directions. One travels 25 miles per hour faster than the other. After 2 hours, they are 490 miles apart. find the speed of the faster airplane.

解答

Tw o ai r pl an es l e a v e C hi c a g o^{'} s M i d w a y ai r p or t a t t h e s am e t im e, t r a v e l in g in o pp os i t e d i rec t i o n s . O n e t r a v e l s 25 mi l es p er h o u r f a s t er t han t h e o t h er . A f t er 2 h o u rs, t h ey a re 490 mi l es a p a r t . f in d t h e s p ee d o f t h e f a s t er ai r pl an e .

second plan e^{'} s speed : 110

求解步骤

Translate the problem into an equation:

(x + 25) \cdot 2 + x \cdot 2 = 490

求解

x, (x + 25) \cdot 2 + x \cdot 2 = 490 : x = 110

second plan e^{'} s speed : 110