Question

The sum of first and 21st terms of an arithmetic sequence is 140. a). what is the 11th term. b)write the sequence,if the first term is 10.c) calculate the sum of the first terms of this sequence.d) find tge sum of first 11 terms of the sequence 20,25,30......​

Answer 1

Answer:

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Answer 2

the answer is 70.

first term= a

21st term= a + 20d

11th term= a+ 10d-----------(1)

A.T.Q

a + a + 20d= 140

2a +20d= 140

2(a + 10d)= 2(70)

a + 10d= 70

hence the 11th term is 70

Found this from my friend :