Question

This diagram shows part of a design made by using toothpicks to form triangles. The top level uses 3 toothpicks. The second level uses 6 toothpicks. The third level uses 9 toothpicks, and so on. If you decide to continue the design so that it has 7 levels, how many toothpicks do you need altogether?

Answer 1

Can anyone help?

Answer 2

if you observe the pattern it is increasing by 3 for every level
level 1 2 3 4 5 6 7
number 3 6 9 12 ....
this is in arithmetic progression
of the form a,a+d,a+2d........... where a=first term
d=common difference
n term is given by a+(n-1)d

Answer 3

I think it is 21