Question

In an AP 1st term is 1 and last term is 20 .the 50m of all terms is 399 then n=?

Answer 1

Answer:

What is Atom?

An atom is the smallest unit of ordinary matter that forms a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. Atoms are extremely small, typically around 100 picometers across.

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Answer 2

Answer:

38

Step-by-step explanation:

sum of n terms, sn=n/2(first term+last term)

Here,

sn=399

first term=1

last term=20

then

399=n/2(1+20)

399×2=21n

798=21n

n=798/21

n=38