Question

The sum of the speeds is 720.8 miles per hour. If the speed of the first train is 9.2 mph faster than that of the second train, find the speeds of each

Answer 1

Let the speed of second train = x mph

Speed of first train = (x+9.2) mph

The sum of the speeds is 720.8 mph

$x + (x + 9.2) = 720.8 \\ \\ 2x + 9.2 = 720.8 \\ \\ 2x = 720.8 - 9.2 \\ \\ 2x = 711.6 \\ \\ x = \frac{711.6}{2} \\ \\ \underline{x = 355.8 \: mph}$

$\underline{x + 9.2 = 355.8 + 9.2 = 365 \: mph}$

$\textbf{\red{Speed of first train = 365 mph}} \\ \\ \textbf{\red{Speed of second train = 355.8 mph}}$

Answer 2

Sum and difference problem.

Speed of faster train = (Sum+difference)/2=(720.8+9.2)/2=365 mph

Speed of slower train = (Sum-difference)/2=(720.8-9.2)/2=355.8 mph