Question

2) Find 'n', if S, is sum of all odd numbers from 1 to 150.
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Answer 1

Answer:

5625

Step-by-step explanation:

Clearly, the odd natural numbers from 1 to 150 are 1,3,5,...,149.

This is an AP with first term a=1, common difference d=2 and last term a

n

=l=149.

Let there be n terms in this AP.

Then,

a

n

=149

⇒a

n

=a+(n−1)d

149=1+(n−1)×2

149=1+2n−2

2n=150

∴n=75

∴ required sum =S

n

=

2

n

[a+l]=

2

75

[1+149]=5625