Given, a=45 km/h, y=?, \( \Large t_{1} \) = 4h 48 min and \( \Large t_{2} \) = 3 h 20 min

Using y = \( \Large a\sqrt{\frac{t_{1}}{t_{2}}}=45\sqrt{\frac{4 h \  and \  48 \  min}{3 h \  and \  20 \  min}} \)

= \( \Large 45\sqrt{\frac{\frac{24}{5}h}{\frac{10}{3}h}} \)

= \( \Large 45\sqrt{\frac{24 \times 3}{5 \times 10}} \)

= \( \Large 45 \times \sqrt{1.44}=45 \times 12 \) = 54 km/h