No. of matchsticks used to make 1st square = 4
No. of matchsticks used to make 2nd square = 7
No. of matchsticks used to make 3rd square = 10
So, the pattern that we observe here is 3n + 1
With this pattern, we can easily find the number of matchsticks required in any number of squares.
How many matchsticks will be used in the 40th figure?
3n + 1
3 × 40 + 1
= 121 matchsticks