A car starts with a speed of 20km / hr and accelerates at a rate of 3.4 m/s for 20 seconds. What is the final speed of the car in km/hr?

The relevant formula that we can use in this situation is:

v = v0 + at

where v is the final velocity, v0 is the initial velocity = 20 km/hr, a is acceleration at 3.4 m/s^2 and t is time at 20 seconds

First convert v0 to m/s, v0 = 5.56 m/s

v = 5.56 m/s + 3.4 m/s^2 * 20 s

v = 73.56 m/s

Then convert back to km/hr:

v = 264.82 km/hr