Solve the problem.
-A brick staircase has a total of 19 steps The first step requires 111 bricks. Each successive step requires 4 fewer bricks than the prior one. How many bricks are required to build the staircase?
A)1425 bricks
B)2850 bricks
C)1387 bricks
D)2793 bricks

Question

Quizplus · Accepted Answer

The number of bricks required forms an arithmetic sequence with the first term $a_1 = 111$ and a common difference $d = -4$. The total number of bricks needed can be found using the formula for the sum of an arithmetic series: $S_n = \frac{n}{2}(2a_1 + (n-1)d)$, where $n = 19$. Substituting the values, we get $S_{19} = \frac{19}{2}(2*111 + (19-1)*(-4)) = \frac{19}{2}(222 - 72) = \frac{19}{2} * 150 = 1425$.

Solve the Problem. -A Brick Staircase Has a Total of 19 Steps the 19