Question

In a race from point X to point Y and back, Jack averages 30 miles per hour to point Y and 10 miles per hour back to point X. Sandy averages 20 miles per hour in both directions. Between Jack and Sandy, who finished first?

Answer 1

Answer:

Sandy will finish the race first.

Step-by-step explanation:

Let D be the total one sided distance in miles, ( between X and Y ),

We know that,

$Speed =\frac{Distance}{Time}$

$\implies Time =\frac{Distance}{Speed}$

Since, from point X to point Y and back, Jack averages 30 miles per hour to point Y and 10 miles per hour back to point X.

So, the total time taken by Jack = $\frac{D}{30}+\frac{D}{10}$

$=\frac{D+3D}{30}$

$=\frac{4D}{30}$

$=0.1333D$

Also, Sandy averages 20 miles per hour in both directions,

So, the total time taken by Sandy = $\frac{D}{20}+\frac{D}{20}$

$=\frac{D+D}{20}$

$=\frac{2D}{20}$

$=\frac{D}{10}$

$=0.10D$

∵ 0.133D > 0.10D

Hence, Sandy will finish the race first.