Answer
a). Option (1) has the greatest speed.
b). 33.6 mi/hr.
Work Step by Step
a). (1)= 1 m/s
(2) = 1 km/hr = 1000 m / 3600 s =$ \frac{1000}{3600} m/s$ $\approx 0.3 m/s $
(3) = 1 ft/s = 0.3048 m/s
(4) = 1 mi/hr = 1.609 km/3600 s= $\frac{1.609\times 1000 m}{3600 s}\approx0.4 m/s$
Hence, option (1) is greatest.
b). $15 m/s = 15 \times\frac{\frac{1mi}{1609}}{\frac{1 hr}{3600}}=15\times\frac{3600}{1609}=33.6 \,mi/hr$
