Making triangle patterns

This task is about shape patterns and how they change.
In this task you:
  1. use straws to build a pattern,
  2. make a prediction about how many straws you need for more patterns and
  3. write an explanation.
 
   

    Y  /  N

a) Your teacher will give you 3 straws. Use these straws to make a triangle.
 
b) Your teacher will give you 2 more straws. Add these 2 straws onto the triangle you have made so there are 2 triangles touching side by side.
 
c) Your teacher will give you 2 more straws. Now add these 2 straws onto what you have already made to make 3 triangles touching side by side.
 
d) How many straws did you use altogether to make 3 triangles? __________
 
 
e) How many straws would you need altogether to make 4 triangles? __________
 
f) How many straws would you need altogether to make 5 triangles? __________
 
g) i)
 
ii)
How many straws would you need altogether to make 10 triangles? __________
 
How did you work this out?