A person travels from New York to Washington at the rate of 45 km per hour and
comes backs to the New York at the rate of 55 km per hour. What is his average
speed for the whole journey?

The average speed for the whole journey is 49.5 miles per hour.

Explanation:

Step 1 :

Here, both the ways, he covers the same distance.  Then, the formula to find average speed is

=  2xy / (x+y)

Step 2 :

x > Rate at which he travels from New York to Washington  

x  =  45

y > Rate at which he travels from New York to Washington  

y  =  55

Step 3 :

So, the average speed is

=  (2 ⋅ 45 ⋅ 55) / (45 + 55)

=  4950 / 100

=  49.5

the answer for apex is the lowest

multiply 2kg by latent heat of vap