Had a tempo driver gone 10 km/h faster, he would have taken 1 hour less to cover 200 km. What was his actual speed?

Explanation

1. 01

   $\frac{200}{v} - \frac{200}{v+10} = 1$, which simplifies to $v(v+10) = 2000$.

2. 02

   Try $v = 40$: $40 \times 50 = 2000$. It fits.

3. 03

   Check: 200 km takes 5 h at 40 km/h and 4 h at 50 km/h, 1 hour less.