Two arithmetic series are such that their common differences are 9 and 3 respectively. if their first terms are 2 and 5 respectively, find the number of terms of each series that would give a common sum
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Answer:
number of terms=n=2
Step-by-step explanation:
in first series
a=2
d=9
in second series
a=5
d=3
Sn=n/2(2a+n-1)d
equalise Sn for first series and second series
therefore we get
n/2(2.2+(n-1)9)=n/2(2.5+(n-1)3)
4+9n-9=10+3n-3(on both sides n/2 get cancelled)
9n-5=3n+7
9n-3n=7+5
6n=12
n=2
sum of two terms are equal for each series
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