Time and Distance Practice Test 4 with solutions

Average speed = $\frac{2\mathit{x}\mathit{y}}{\mathit{x}+\mathit{y}}$
= $\frac{2\times 72\times 56}{72+56}$
= 63 km/hour
Alternative Method:
By using alligation rule,
Let, the average speed = x
The ratio of speeds = 72 : 56 = 9 : 7
So, ratio of time taken = 7 : 9
$\frac{72-\mathit{x}}{\mathit{x}-56}$ = $\frac{9}{7}$
504 - 7x = 9x - 504
16x = 1,008
x = 63
So, the average speed = 63 km/hour.