Question

WHICH TERM OF THE A. P.
3,15,27,39............. WILL BE 120 MORE THAN ITS 21st TERM ?



Heys
Meri pyaari kaju
Meri Pyaari sis aaru​

Answer 1

Answer:

εηηο❤

____________

a=3,d=12

Now ,ATQ

an=120 +a21

an=120 + a +20d

a +(n-1)d = 120 + a +20d

cancel a each side ........

(n-1)12 = 120+ 20(12)

12n-12=120+240

12n=372

n=31

Hence the term will be 31st term

hope helps

Answer 2

αɳรωεɾ

The 31st term will be 120 more than 21st term of given AP.

รσℓµƭเσɳ

Given series of AP is :-

3, 15 ,27 , 39 ........

So from this AP we got

→a ( 1st term ) = 3

→d ( common difference ) = 12 .

Now firstly we will find 21st term of AP.

As we know that:-

an = a + ( n-1)d , So applying this.

a21 = 3 +(21-1)12

a21 = 3 + 240

a21 = 243

So the 21st term of AP is 243 .

Now according to the question 120 more than 21st term will -

243 +120 = 363

Now we have value of term ( 363) and have to find its place. So,

363 = 3 +( n-1 )12

363 -3 = 12n -12

360 +12 = 12n

372 = 12n

n = 31

Place of term is 31st

So 21st +120 = 31st place of AP