Answer:
fourth option
Step-by-step explanation:
Common difference is given by difference of two consecutive term
d = nth term - (n-1)th term
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for all the series lets take second term as nth term
and first term as (n-1)th term
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for first series
n th term = -3 1/2 = -3.5
(n-1)th term = -5
therefore
d= -3.5 -(-5) = -3.5 +5 = 1.5
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for second series
n th term = 4 1/2 = 4.5
(n-1)th term = 2 1/2 = 2.5
therefore
d= 4.5 -(2.5) =2
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for third series
n th term = 3
(n-1)th term =1.5
therefore
d= 3 - 1.5 = 1.5
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for fourth series
n th term = -1.5
(n-1)th term = -4
therefore
d= -1.5 -(-4) = -1.5 + 4 = 2.5 = 2 1/2
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Thus, based on above solution option four has common difference of 2 1/2
