Question

What is the difference between the sum of 1st 20 terms and the next 20 terms of the arithmetic sequence 6, 10 , 14, ...

Answer 1

Step-by-step explanation:

6 , 10 , 14 , …… is the AP

1st term 6 , common diff=10–6=4

21 st term = 6+(21–1)×4=86

20 th term=86–4=82

40 th term = 6+(40–1)×4=6+39×4=

=156+6=162

sum of 21 st to 40 th term ie 20 terms

=(86+162)20/2=248×10=2480

sum of first 20 terms

=(6+82)×20/2=880

difference =2480–880=1600