Question

A car that travels at 6.3 km/hr for 2.0 hrs, at 5.7 for 1.0 hr and at 6.6 for half an hour. What is its average speed?

Answer 1

Solution.

$v_1=6.3 km/hr;$

$t_1=2.0hr;$

$v_2=5.7 km/hr;$

$t_2=1.0hr;$

$v_3=6.6 km/hr;$

$t_3=0.5 hr;$

$v_{average}=\dfrac{l_1+l_2+l_3}{t_1+t_2+t_3};$

$l_1=v_1\sdot t_1=6.3\sdot 2.0=12.6km;$

$l_2=v_2\sdot t_2=5.7\sdot1.0=5.7km;$

$l_3=v_3\sdot t_3=6.6\sdot0.5=3.3km;$

$v_{average}=\dfrac{12.6+5.7+3.3}{2.0+1.0+0.5}=6.17 km/hr;$

Answer: $v_{average}=6.17 km/hr.$