Question

1. In an arithmetic progression, the first term is -13, the 20th term is 82 and the last term is 112.

a Find the common difference and the number of terms.
b Find the sum of the terms in this progression.​

Answer 1

Answer:

too

Step-by-step explanation:

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Answer 2

Answer:

first term is -13 (a)

20th term is 82(T 20th)

last term is 112(T nth)

a. Find the common difference(d) and the number of terms(n)

T 20th = a+ 19d

82 = -13 +19d

82+13 = 19d

95/19 = d

d = 5

and

T nth = a+ (n-1)d         (we have to find n : the number of terms)

112 = -13 +5n -5

112 =-18 +5n

112+18 = 5n

130/5 =n

n(number of terms) = 26

b. Find the sum of the terms(Sn) in this progression

Sn = n/2 × (first term+ last term)

= 26/2×(-13 +112)

= 13×(109)

= 10417

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