Solve.
-A brick staircase has a total of 12 steps The bottom step requires 109 bricks. Each successive step requires 5less bricks than the prior one. How many bricks are required to build the staircase?
A)978 bricks
B)1,638 bricks
C)1,956 bricks
D)948 bricks

Question

Quizplus · Accepted Answer

The total number of bricks required can be found using the formula for the sum of an arithmetic series. The first term (a) is 109 bricks, the common difference (d) is -5 (since each step requires 5 fewer bricks), and the number of terms (n) is 12. The sum (S) of an arithmetic series is given by S = n/2 [2a + (n-1)d]. Plugging in the values, we get S = 12/2 [2(109) + (12-1)(-5)] = 6 [218 - 55] = 6 * 163 = 978.

Solve. -A Brick Staircase Has a Total of 12 Steps the the Bottom