Answer: 1547 bricks are required to build the staircase.
Explanation:
We are given:
Number of bricks in the first step,
= 131
Number of bricks in the second step,
= 131 - 5 = 126
Number of bricks in the third step,
= 126 - 5 = 121
Sequence become:
131, 126, 121, .....
These are in arithmetic progression where a = 131 and d (common difference) = -5
To calculate the sum of an AP, we use the formula:
where,
n = number of terms = 17
Putting values in above equation, we get:
Hence, 1547 bricks are required to build the staircase.