Advertisements
Advertisements
प्रश्न
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
How many bricks are required to build the stair case?
उत्तर
100 + 98 + 96 + 94 + … 30 steps.
Here
a = 100
d = – 2
n = 30
∴ Sn = `"n"/2` (2a + (n – 1)d)
S30 = `30/2` (2 × 100 + 29 × – 2)
= 15(200 – 58)
= 15 × 142
= 2130
No. of bricks required to build the stair case are 2130.
APPEARS IN
संबंधित प्रश्न
Find the sum of the following
102, 97, 92, … up to 27 terms.
How many consecutive odd integers beginning with 5 will sum to 480?
Find the sum of first 28 terms of an A.P. whose nth term is 4n – 3
The sum of first n terms of a certain series is given as 2n2 – 3n. Show that the series is an A.P.
The 104th term and 4th term of an A.P. are 125 and 0. Find the sum of first 35 terms
Find the sum of all natural numbers between 602 and 902 which are not divisible by 4.
Find the sum `[("a" - "b")/("a" + "b") + (3"a" - 2"b")/("a" + "b") + (5"a" - 3"b")/("a" + "b") + ... "to" 12 "terms"]`
An A.P. consists of 31 terms. If its 16th term is m, then the sum of all the terms of this A.P. is
In an A.P., the first term is 1 and the common difference is 4. How many terms of the A.P. must be taken for their sum to be equal to 120?
If A = 265 and B = 264 + 263 + 262 …. + 20 identify of the following is true?
