Question

which term of the sequence 3,8,13... is 78

Answer 1

Heya!!
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◾Given Sequence is => 3 , 8 , 13 ...............


Here ,
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✔First term a = 3

✔Common Difference d = 5

✔The Nth term An = 78

✔We need to find n => ?


Using the formula for An

An = a + ( n -1 ) d

78 = 3 + ( n - 1 ) 5

78 - 3 = ( n - 1 ) 5

75 = ( n - 1 ) 5

75/5 = ( n - 1 )

n - 1 = 15

n => 16


⭐Hence it's the 16th term !!



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Answer 2

AP = 3 , 8 , 13 , ..........



Here,


First term ( a ) = 3


Common difference ( d ) = 5



Tn = 78



a + ( n - 1 ) × d = 78



3 + ( n - 1 ) × 5 = 78


3 + 5n - 5 = 78



5n = 80


n = 16


Hence,

16th term of the given AP will be equal to 78.