Physics hot air balloon problem

[jodo658]

Physics problem...!

A hot air balloon is ascending straight up at a constant speed of 7.50 m/s. When the balloon is 15.0 m above the ground, a gun fires a pellet straight up from ground level with an initial speed of 38.0 m/s. Along the paths of the balloon and the pellet, there are two places where each of them has the same altitude at the same time. How far above ground level are these places? Enter the answers in the ascending order.

can anyone help me with this problem?? We just started one dimensional motion and the kinematic equations. and I'm trying to figure this one out ..but I can't...I figured out all my other ones and I'm pretty good at Physics..but I don't know why I can't figure this one out

 

[tiny-tim]

Welcome to PF!

A hot air balloon is ascending straight up at a constant speed of 7.50 m/s. When the balloon is 15.0 m above the ground, a gun fires a pellet straight up from ground level with an initial speed of 38.0 m/s. Along the paths of the balloon and the pellet, there are two places where each of them has the same altitude at the same time. How far above ground level are these places? Enter the answers in the ascending order.

Hi jodo658! Welcome to PF!

Hint: What is the height of each at time t?

 

[Sakha]

Using the formula d=V_ot+.5at², you can see you have 2 unknows: d and t, but you also have 2 equation, so you can solve it.