Question

1 which team of the AP : 3, 8, 13, 18. ... ?
a = 3 ,d = 5, an=78 n = ? ​

Answer 1

Answer:

$a = 3 \\ d = 5 \\ an = 78 \\ an = a + (n - 1)d \\ 78 = 3 + (n - 1)5 \\ 78 - 3 = 5n - 5 \\ 75 + 5 = 5n \\ n = \frac{80}{5} \\ n = 16$

Step-by-step explanation:

an=a+(n-1)d

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Answer 2

Given,

first term(a)=3

common difference(d)=5

nth term(an)=78

no. of terms

an=a+(n-1)d

78=3+(n-1)5

78=3+5n-5

78=-2+5n

5n=78+2

5n=80

therefor, n=16