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# C2 A level maths question help watch

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1. How would you do a question like this?
Given the first term, a, the common difference, d, and the last term, l, find the sum of the following arithmetic series:
a=8, d=3, l=65
2. (Original post by NeeIam)
How would you do a question like this?
Given the first term, a, the common difference, d, and the last term, l, find the sum of the following arithmetic series:
a=8, d=3, l=65
Use the formula

Sn= n/2(a+l)

U also have to find n 65=a+(n-1)d
3. (Original post by Xenon17)
Use the formula

Sn= n/2(a+l)

U also have to find n 65=a+(n-1)d
I don't understand what I'm meant to do with the 2nd formula, how to find n
4. (Original post by NeeIam)
I don't understand what I'm meant to do with the 2nd formula, how to find n
n is between the ( and-
5. (Original post by Xenon17)
n is between the ( and-
Never mind I got it thank you!

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