A brick staircase has a total of 17 steps, with the first step requiring 118 bricks. Each successive step requires 5 less bricks than the prior one. How many bricks are required to build the staircase?
+23245 To find the total number of bricks, you can use this formula: Sum = n(t1 + tn) / 2
where n = number of numbers = 17
t1 = first number = 118
tn = last number = ??
To find tn, you can use the formula: tn = t1 + (n - 1)·d
where d = common difference = -5
---> tn = 118 + (17 - 1)·(-5) = 38
---> Sum = 17(118 + 38)/2 = 1326 bricks.
