how many terms of the series 18+15+12+.... when added together will give 45?
Answers
Answered by
3
in this series
a=18
D=-3
so the next two teams are 9 and 6
so the addition of 18+15+12=45
3 terms of the series when added will give 45
a=18
D=-3
so the next two teams are 9 and 6
so the addition of 18+15+12=45
3 terms of the series when added will give 45
Answered by
10
let no of required term is n.
then
Sn= n/2[2a+(n-1)d]
45=n/2[2×18+(n-1)(-3)]
45=n/2(39-3n)
90=39n - 3n^2
3n^2 -39n +90=0
after solving...
n = 10 & 3
then
Sn= n/2[2a+(n-1)d]
45=n/2[2×18+(n-1)(-3)]
45=n/2(39-3n)
90=39n - 3n^2
3n^2 -39n +90=0
after solving...
n = 10 & 3
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