A sequence of odd numbers is grouped the following way;

$\displaystyle \{1\},\:\:\{3,5,7\},\:\:\{9,11,13,15,17\},\:\:\{19 ,21,23,25,27,29,31\},\:\:...$

How many numbers are there in the $\displaystyle n$th group?

(this seemed straightforward enough. By observation; $\displaystyle 2n-1$)

How many numbers are there from the $\displaystyle 1$st group to the $\displaystyle (n-1)$th group?

(this is where everything goes downhill for me, would be great to get some help...)

What is the first number in the $\displaystyle n$th group?

What is the sum of all the numbers in the $\displaystyle n$th group?

What is the sum of all the numbers in the $\displaystyle 10$th group?

Once again, any help appreciated.