Question

A brick staircase has a total of 30 steps. The bottom step requires 100 bricks. Each
successive step requires two bricks less than the previous step.
(i) How many bricks are required for the top most step?
(ii) How many bricks are required to build the stair case?
a
f
AD 1
​

Answer 1

Answer:

[i]42

[ii]2130

Step-by-step explanation:

a=100

n=30

d=-2

t30=?

s30=?

1] tn=a+[n-1]d

t30=100+29[-2]

t30=100-58

t30=42

2]sn=n/2[2a+[n-1]d]

  S30=30/2[200+-[58]]

=15*142

=2130

Answer 2

42 Bricks required for top most step and 2130 bricks required to build the stair case

Step-by-step explanation:

100 bricks required for Bottom step

Total Step = 30

each successive step needs 2 brick less than the previous step​

This is an AP

a = 100

d = - 2

n = 30

bricks are required for the top most step that means 30th step

= a + (30-1)d

= 100 + 29(-2)

= 100 - 58

= 42

42 Bricks required for top most step

bricks required to build the stair case

= (n/2)(a + L)

= (30/2)(100 + 42)

= 15 * 142

= 2130 Bricks

Learn more:

A brick staircase has a total of 30 steps

https://brainly.in/question/13997590

In an A.P if sum of its first n terms is 3n square +5n and it's Kth term ...

https://brainly.in/question/8236011

If the sum of m terms of an AP is n and sum of n terms is m, then ...

https://brainly.in/question/7562249