Arithmetic series- sum of first ten terms is 460

I am questioning my approach to this two-part question. Can someone verify if my approach is right, please?

See attached:

I am applying simultaneous equations but I am using a value taken from the sum of terms and a sum from an nth term.

I'm just unsure if that's the right thing to do but I have no information to work from...

I have tested it by finding a and seeing if it finds the same value as the given term in part b and then applying the difference to find a sequence of 1,11,21,31,41,51,61,71,81,91 and they all sum to the given term in part a.

I'm just doubting myself

(edited 5 months ago)

Reply 1

mqb2766

Looks fine. You have two variables to determine and two pieces of information (linear equations).

Reply 2

KingRich

Original post by mqb2766

Looks fine. You have two variables to determine and two pieces of information (linear equations).

Fantastic. The variables are both the same whether used in the summation formula or nth term, so I figured, surely I can but I wasn’t certain. Thank you for confirming