Pyramid pattern

This task is about making patterns and finding a rule.
Your teacher will show you how to make a pyramid pattern.
 
 

Y    N

a)
 
Firstly, make the next size pyramid up.
 
b)
 
Now make the next size pyramid up.
 
c)
Altogether how many triangles did you need to make the last pyramid pattern? __________
 
d)
i)
  
 

ii)
How many triangles would you need to make the next size up from this pyramid pattern?
 
__________
  
How did you work this out?