Mode: The class which has the highest frequency.
In this case, class interval 40-50 is the modal class.
Now,
Lower limit of modal class, l = 40
h = 10
f1 = 20
f0 = 12
f2 = 11
We know that,
Mode = l + ((f1 - f0) / (2f1 - f0 - f2)) * h
= 40 + ((20 - 12) / (2(20) - 12 - 11)) * 10
= 40 + (8 / (40 - 23)) * 10
= 40 + (8 / 17) * 10
Mode ≈ 44.7
Hence, the mode of the given data is 44.7 cars.