Question

A brick staircase has a total of 16 steps The bottom step requires 112 bricks. Each successive step requires 4 fewer bricks than the prior one. How many bricks are required to build the staircase?

Answer 1

you are finding the sum of 16 terms of an arithmetic sequence where
a = 112
d = -4
n = 16

S₁₆ = (16/2)[2(16) + 15(-4) ]
= .....

Answer 2

-224