Answer:
[tex]\frac{3m + 4.2M}{m+M}[/tex]
Where m is Ashley's mass and M is Miranda mass, in kg.
Explanation:
Let m be Ashley's mass and M be Miranda mass, in kg.
By the law of momentum conservation, after the hop on, we have the following momentum equation:
mv + MV = (m + M)S
where v = 3m/s is Ashley speed before the hop on, V = 4.2 m/s is Miranda's speed before the hop on. And S is their speed after
[tex]S = \frac{mv + MV}{m+M} = \frac{3m + 4.2M}{m+M}[/tex]
