The 1st pattern consists of 4 dots. For any +ve integer n, the (n+1)th pattern is formed by adding 3 dots to the nth pattern. Find the number of dots in the 8th pattern.

Question

anonymous · Answer

@ajprincess

anonymous · Answer

@amistre64

amistre64 · Answer

4
4 + 3
4 + 3 + 3
4 + 3 + 3 + 3
4 + 3 + 3 + 3 + 3

etc

amistre64 · Answer

4 + 3(n-1)  is what it looks like to me

anonymous · Answer

25?

anonymous · Answer

How about this question:

the 1st pattern consists of 1 do. For any +ve integer n, the (n+1)th pattern is formed by adding n dots to the nth pattern. Find the number of dots in the 8th pattern.

amistre64 · Answer

1: 1 
2: 1 + 1 + 1
3: 1 + 1 + 1 + 1 + 1 + 1
4: 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1 + 1


1 
3
6
10
15
21

its the triangle numbers

amistre64 · Answer

0  1  3   
  1  2   
    1

1+2n+n(n-1)/2

amistre64 · Answer

my first idea was better, start with the zero:

n+n(n-1)/2