Question

A high school student has started a new job. He plans to save $1 the first week, $2 the second week, $4 the third week, and $8 the fourth week. If this pattern of savings could continue, how much would he save the tenth week?
a.
$150
c.
$400
b.
$370
d.
$512

Answer 1

D is the answer it must be it

Answer 2

If you already know that you have . . . 

1$ after week 1
2$ after week 2
4$ after week 3
8$ after week 4

 . . . You can then tell that every week the money you save doubles (times 2) 

So to continue . . . . 
16$ after week 5
32$ after week 6
64$ after week 7
128$ after week 8
256$ after week  9
512$ after week 10 

You will then know that after ten weeks u will have 512$ which is answer choice D. 

Hope this helps! :)