Question

1. Consider the arithmetic sequence:7,11,15,..........

a) Find its 20th term?

b) Calculate the sum of first 20 terms?​

Answer 1

Answer:

a)83

b)900

Step-by-step explanation:

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Answer 2

Answer:

a) 83

b) 900

Step-by-step explanation:

a) in this A.P.

   a = 7 d = 11-7 = 4

t(20) = a+19d

   7 + 76

 = 83

b) sn = $\frac{n}{2}$[2a + (n-1)d]

 10(14+76)

10(90)

900

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