solving arithmetics squence

[jianhong12]

 

[Dr.Peterson]

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What formula(s) do you know for arithmetic sequences/series? What happened when you tried using them?

 

[tkhunny]

Write out an expression that represents the answer.

If there are only two rows, 600 + 660 = 70,800, for example. Obviously, this is preposterous and will not lead you to a solution. What needs to be changed to make it other than preposterous? Obviously, again, two rows is an nsufficient number pf rows. How do you create an expression for SOME NUMBER of rows?

 

[jianhong12]

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Welcome to our tutoring boards! :) This page summarizes main points from our posting guidelines. As our name implies, we provide math help (primarily to students with homework). We do not generally post immediate answers or step-by-step solutions. We don't do your homework. We prefer to help...

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What formula(s) do you know for arithmetic sequences/series? What happened when you tried using them?

arithmetic formula for sum of first n term = $$\frac{n}{2} \lbrack 2a+(n-1)d \rbrack$$when a means first term is 660 and d means common difference is 660,
$$\frac{n}{2}\lbrack 2(660)+(n-1)(660) \rbrack = 70800$$ ????

 

[lev888]

arithmetic formula for sum of first n term = $$\frac{n}{2} \lbrack 2a+(n-1)d \rbrack$$when a means first term is 660 and d means common difference is 660,
$$\frac{n}{2}\lbrack 2(660)+(n-1)(660) \rbrack = 70800$$ ????

Please take another look at the common difference.
After you fix the equation solve it for n.