Desmond builds a set of towers out of blocks. The table shows the number of blocks in each tower.

Question

Tower #

1



2



3



4



5

Number of blocks

5



10



20



40



80

Question

Which explicit formula correctly represents the number of blocks, a Subscript n Baseline
, in terms of the tower number, n

?
Answer options with 4 options
A.

a Subscript n Baseline equals n plus 80

B.

a Subscript n Baseline equals 2 n plus 5

C.

a Subscript n Baseline equals 5 left-parenthesis 2 right-parenthesis Superscript n minus 1 Baseline

D.

a Subscript n Baseline equals 10 left-parenthesis 5 right-parenthesis Superscript n Baseline

Answer 1

The correct answer is B.

The pattern in the number of blocks in each tower is that each tower has double the number of blocks compared to the previous tower. We can represent this pattern using the formula a_n = 2n + 5, where n is the tower number.