Math, asked by roop1992, 1 year ago

श्रेणी 1+2+3.... के कितने पदों का योगफल 5050 होगा ?​

Answers

Answered by luckyjoshi615
7

sum of natural numbers= n×(n+1)/2=5050

n^2+n-10100=0

n^2+101n-100n=0

n=100 or -101

n can't be -101 because ek shrebi mein rinatmak pad NAHI HO SKTE....

so n=100

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Answered by erinna
5

The required number of terms is 100.

Step-by-step explanation:

We need to find number of terms in the series 1+2+3+.., whose sum is 5050.

First term = 1

Common difference = 2-1 =1

Sum n terms of an AP is

S_n=\dfrac{n}{2}[2a+(n-1)d]

where, a is first term and d is common difference.

Substitute a=1, d=1 and S_n=5050

5050=\dfrac{n}{2}[2(1)+(n-1)(1)]

10100=n[2+n-1]

10100=n(1+n)

10100=n^2+n

n^2+n-10100=0

Splitting the middle term we get

n^2+101n-100n-10100=0

n(n+101)-100(n+101)=0

(n+101)(n-100)=0

n=-101,100

Number of terms can not be negative. So, n=100.

#Learn more

Sum of first n terms of an ap is 2,4,6,.... Is 240 then the value of n.

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