Question

Which term of the A.P. 3, 15, 27, 39, ... will be 120 more than its 21st term?

Answer 1

Answer:

31st term of the A.P  3, 15, 27, 39, ... will be 120 more than its 21st term

Step-by-step explanation:

Given :  

A.P 3, 15, 27, 39, ...

first term , a = 3 , common difference , d = 15 - 3 = 12

nth term = 120 + a21

 

a + (n -1)d = 120 + a21

[nth term = a + (n -1)d]

3 + (n - 1)12 = 120 + a + (21 - 1) d

3 + 12n - 12 = 120 + 3 + 20 ×  12

-9 + 12n  = 120 + 3 + 240

-9 + 12n  = 123 + 240

-9 + 12n   = 363

12n = 363 + 9

12n = 384

n = 372/12

n = 31

Hence, 31st term of the A.P  3, 15, 27, 39, ... will be 120 more than its 21st term

HOPE THIS ANSWER WILL HELP YOU...

Answer 2

Answer:-

Refer the attachment