Question

A fireplace contains 46 bricks along its bottom row. If each row above decreases by 4 bricks, what is the function that shows the bricks on the 12th row?

Answer 1

n-th term of the arithmetic progression is given by

$$a_n=a_1+(n-1)d$$

$$a_1=46$$

$$d=-4$$

$$a_n=46+(n-1)(-4)=46-4n+4=50-4n$$

n=12

$$a_{12}=50-4\cdotp12=2$$

Answer: 2