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?

1326 bricks

Step-by-step explanation:

Step 1 will have 118 bricks

Step2 will be 118-5=113 bricks

Step 3 will have 118-(2*5)=108 bricks

Step 17 will have 118-(16*5)=38 bricks

The number of bricks in first step is given as 118+5(n-1) where n starts as 1

At any step n, the number of bricks will be 118+5(n-1)

The sum of the bricks can be found by

Sum=½n(n(1)+n(17))

Since n(1)=118 bricks and n(17) is 38 bricks

Sum=½*17(118+38)=1326 bricks

$12. that is my answer.

answer: all of the odd numbers were opened

the first person was the one that was opening all of the lockers. since one is odd, this causes all of the odd number lockers to be opened in the end.