The-first-term-of-an-arithmetic-series-is-7-and-the-last-is-70-and-the-sum-is-385-find-the-number-of-terms-in-the-series-and-its-common-difference-

Question Number 192450 by Mastermind last updated on 18/May/23

$$\mathrm{The}\:\mathrm{first}\:\mathrm{term}\:\mathrm{of}\:\mathrm{an}\:\mathrm{arithmetic}\:\mathrm{series} \\ $$$$\mathrm{is}\:\mathrm{7}\:\mathrm{and}\:\mathrm{the}\:\mathrm{last}\:\mathrm{is}\:\mathrm{70}.\:\mathrm{and}\:\mathrm{the}\:\mathrm{sum}\:\mathrm{is} \\ $$$$\mathrm{385}.\:\mathrm{find}\:\mathrm{the}\:\mathrm{number}\:\mathrm{of}\:\mathrm{terms}\:\mathrm{in}\:\mathrm{the} \\ $$$$\mathrm{series}\:\mathrm{and}\:\mathrm{its}\:\mathrm{common}\:\mathrm{difference}. \\ $$

Answered by AST last updated on 18/May/23

$$\frac{{n}\left(\mathrm{77}\right)}{\mathrm{2}}=\mathrm{385}\Rightarrow{n}=\mathrm{10};\:\mathrm{7}+\mathrm{9}{d}=\mathrm{70}\Rightarrow{d}=\mathrm{7} \\ $$

Terms of Service
Privacy Policy
Contact: info@tinkutara.com