Question

200 logs are stacked in the following manner 20 logs in boltom, ,
1,9 the next row, 18 in the row next to it soon in how many rows are legs obtain and how many logs are in the top of row

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Answer 1

Answer:

It is an AP such that a=20 & d=−1

S

n

=200

⇒200=

2

n

[2(20)+(n−1)(−1)]

⇒400=n[40+1−n]

⇒n

2

−41n+400=0

⇒n

2

−25n−16n+400=0

⇒(n−25)(n−16)=0

So n=16 or n=25

T

16

=a+15d=20−15=5

T

25

=a+24d=20−24=−4

Since T

25

is not possible.

∴ n=16 & 5 logs are placed in the top row