Question

I need help with number 6c

Answer 1

Remark

Let's assume that each square consists of 4 matchsticks. If this is incorrect, leave a note. We can't really see how many match sticks make up a square, so it makes 6c hard.

Solution

First write the number of squares in the nth windmill.

d = 4 (that's derived from 13 - 9 which are the second and third term.

n = n

a = 5

an = a + (n - 1)*d

an = 5 + (n - 1)*4

Now each square is made up of 4 matchsticks.

So you need to multiply "an" by 4 to get the number of matchsticks.

an_match = 4*[5 + (n -1)*4]         Remove the inner brackets

an_match = 4*[5 + 4n - 4]

an_match = 4*[4n - 1]     Remove the square brackets.

an_match = 16n  - 4  <<<< Answer