Question

Gary draws this sequence of patterns of white and grey squares. The sequence is continued. How many grey squares will there be with 16 white squares?

Answer 1

Answer:

20 gray squares

Step-by-step explanation:

Given

See attachment for squares

Required

Number of gray squares when white = 16

First, we calculate the equation that represents both squares.

The white squares

$a = 2$ --- initial

$d = 4 - 2 = 6 - 4$

$d = 2$ -- difference between successive gray squares

So, the nth term is:

$W_n = a + (n - 1)d$

$W_n = 2 + (n - 1)*2$

$W_n = 2 + 2n - 2$

$W_n = 2n$

The gray squares

$a = 6$ --- initial

$d = 8-6=10-8$

$d = 2$ -- difference between successive gray squares

So, the nth term is:

$G_n = a + (n - 1)d$

$G_n = 6 + (n - 1) *2$

$G_n = 6 + 2n - 2$

$G_n = 4 + 2n$

When the white squares is 16

$W_n = 16$ --- Calculate n

$W_n = 2n$

$16 = 2n$

$8 = n$

$n = 8$

To get the number of gray squares;

Substitute $n = 8$ in $G_n = 4 + 2n$

$G_n = 4 + 2 * 8$

$G_n = 20$