Week 1 – My Arithmetic Sequence

S=t_{1}+ t_{2}+ t_{3}+ t_{4}+ …..

t_1= 20

Common difference: + 10

What’s the t_{250} and What’s the S_250

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Solution:

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t_n=t_1+(n-1)d

t_{250}=20+(250-1)10=2510

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t_{1}=20

t_{2}=20+20+(10)=50

t_{3}=20+20+(10)+20+(10)+(10)=90

t_{4}=20+20+(10)+20+(10)+(10)+20+(10)+(10)+(10)=140

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t_{250}= 20+20+(10)+20+(10)+(10)+20+(10)+(10)+(10)+***

=\frac{n}-2 x (20 + 510)

=\frac{n}-2 x 530

=56250

In conclusion, t_250 = 2510 and S_250 = 56250