Chapter 12, Problem 65RE

(a)

To determine

To find: The number of bricks required for the top step .

Answer to Problem 65RE

The number of brick required for the top step is $8$ .

Explanation of Solution

The number bricks required for the top step is calculated as,

  $\begin{array}{c}{a}_{\text{Top}}=80+\left(25-1\right)\left(-3\right)\\ =80-72\\ =8\end{array}$

Therefore, The number of brick required for the top step is $8$ .

(b)

To determine

To find: The number of bricks required for the staircase .

Answer to Problem 65RE

The number of brick required for the staircase is $1100$ .

Explanation of Solution

The number bricks required for the staircase is calculated as,

  $\begin{array}{c}{S}_{Full}=\frac{25}{2}\left(2\cdot 80+\left(25-1\right)\left(-3\right)\right)\\ =\frac{25}{2}\left(160-72\right)\\ =25\cdot 44\\ =1100\end{array}$

Therefore, The number of brick required for the staircase is $1100$ .