Question

ii. Sum of 1 to n natural numbers is 55, then find the value of n.
The natural numbers from 1 to n are 1,2,3,...
The above sequence is an A.P.​

Answer 1

Answer:

the value of n is 10,.

As 1+2+3+4+5+6+7+8+9+10=55

done this by 10 ×11 /2

Answer 2

Answer:

10

Step-by-step explanation:

S

n

=

2

n

[2a+(n−1)d]

⇒55=

2

n

[(2×1)+(n−1)(1)]

⇒55=

2

n

(2+n−1)

⇒55=

2

n(n+1)

⇒55×2=n

2

+n

⇒n

2

+n=110

⇒n

2

+n−110=0

⇒n

2

+11n−10n−110=0

⇒n(n+11)−10(n+11)=0

⇒n+11=0,n−10=0

⇒n=−11,n=10

Thus, ignoring the negative value of n, we have n=10.

Hence, n=10.

Hope this helps