Question

how many terms are there in the ap 4,11,18.......81?

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Answer 1

Answer:

an= 81

a= 4

d = 11-4=7

an= a+(n-1)d

81= 4+ (n-1)7

81-4 = (n-1)7

77/7 = n-1

11 = n-1

11+1 = n

n= 12

Answer 2

Answer:

$\huge\star\underbrace{\mathtt\red{⫷❥ᴀ᭄} \mathtt\green{n~ }\mathtt\blue{ §} \mathtt\purple{₩}\mathtt\orange{Σ} \mathtt\pink{R⫸}}\star\:$

Step-by-step explanation:

☆Given=>A.P=4,11,18......81.

=>a=4

=>d=7

=>an=81.

=>a+(n-1)d=an

=>4+(n-1)7=81

=>(n-1)7=81-4

=>(n-1)7=77

=>(n-1)=77/7

=>(n-1)=11

=>n=11+1

So n=12.

☞So the value of n is 12,hence there are 12 terms in the given A.P

HOPE IT HELPS.