**Context:**

In my textbook it is given: <sub>'momentum' short for 'linear momentum'</sub>:

> Mass = $m$, momentum is $p=mv$. In time $\Delta t$, momentum changes by $\Delta p$, the rate of change of momentum is:

> $$\frac{\Delta p}{\Delta t} = \frac{\Delta(mv)}{t} = m \frac{\Delta v}{\Delta t}$$

**My Doubts:**

1. Isn't a $\Delta$ sign missing beside the $t$ in the second fraction, and thus it should be $\frac{\Delta(mv)}{\Delta t}$ 
2. How did they derive the third fraction from the second. I tried a lot but can't seem to get that.

**My Work:**

I have looked at this question - [How does $F = \frac{ \Delta (mv)}{ \Delta t}$ equal $( m \frac { \Delta v}{ \Delta t} ) + ( v \frac { \Delta m}{ \Delta t} )$?](http://physics.stackexchange.com/questions/24425/how-does-f-frac-delta-mv-delta-t-equal-m-frac-delta-v-del), but it's a totally different equation.

**My Final Question:**

Can someone please clear my doubts about this equation and help me understand how does:

$$\frac{\Delta(mv)}{t} = m \frac{\Delta v}{\Delta t}$$


Thanks a lot !