Atrain accelerates from its metropolitan cruising speed of 22 m/s to its countryside cruising speed of 32 m/s. if it takes the train 142 seconds to do this, what is its acceleration? 10 m/s2 14.2 m/s2 4.4 m/s2 0.07 m/s2

Since it mentions in the problem that it took 142 seconds for 22 m/s to become 32 m/s, one should multiply 142 by the answer choices. This will determine how many m/s2 was needed to get the change in speed. Then it will be added to the 22m/s to see what is closest to 32 m/s. 

142*10 = 1420+22 = 1442. Too much.
142*14.2 = 2016.4+22 = 2038.4. Too much. Even rounding doesn't do it justice, of course.
142*4.4 = 624.8+22 = 646.8. Too much. Rounding won't work here, either.
142*0.07 = 9.94+22 = 31.94. This is the closest out of all of them, and when rounded it comes up as 32. 

So, the answer would be 0.07 m/s2.

Wavelength divides in half and speed stays the same.