Hello. First time here. When a population grows by 30%, you actually add the 30% of 150 to 150. It's something like this, 150 + 150*(.30). It's actually the same as 150(1.30). Try solving it on a calculator.

If you multiplied 150(0.3), you would get how much the deer population grew. In this case, it grew by 45 deer, right?

But, to get the total population NOW, you would have to add 45 deer to the 150 deer that were already there. That would get you 195 deer in total.

45 deer were added through population growth, but we still have to consider the 150 deer that were there before. That's why they need to be added.

Doing 150(1.30) saves you the extra step of adding. It already gets you the answer of 195 because it adds that 1. 

150(1.30)

= 150(1) + 150(0.3)

= 150+45

= 195

Doing 150(1.30) combines the adding and multiplying into one step. It's a much easier and quicker method. Hope that helped! :)

That was unbelievably helpful!

I'm copying your answer and putting it into my Math study journal.