Sandra plans to fill a corner of her yard with decorative stones. Each row has seven more stones than the prior row. If there were five stones in the first row, how many stones were used to fill all 36 rows? Using complete sentences, explain the procedure taken to answer this question.

Question

anonymous · Answer

How do I set this up?

anonymous · Answer

36/2 [10 + (36 - 1) x 6

anonymous · Answer

@hartnn

hartnn · Answer

5 stones in 1st row = 1st term = a1 = 5
'how many stones were used to fill all 36 rows ' means we are not asked SUM , we are asked , 36th term of the sequence, got this ?

anonymous · Answer

I got this, so I'll use the sequence formula

anonymous · Answer

the geometric one or the arithmetic one?

hartnn · Answer

yes, you'll need a1 , d, and n for that. 
you know the formula, right ?

hartnn · Answer

which one do you think ?

anonymous · Answer

an = a1 + (n - 1) d

hartnn · Answer

yes, correct.

anonymous · Answer

ok i'm a little nervous!!!!

anonymous · Answer

I'm going to start it by myself and then I'll show you, okay?

anonymous · Answer

How do I plug in the numbers if I'm not given them in the problem?

Would "36" be the first term (a1)?

anonymous · Answer

It doesn't tell me the last term either

hartnn · Answer

5 stones in 1st row = 1st term = a1 = 5

hartnn · Answer

'how many stones were used to fill all 36 rows ' means 36th term is asked , n= 36

anonymous · Answer

5 stones + 7 stones = 12 stones

anonymous · Answer

ok let me solve!!!:))))

hartnn · Answer

yeah, what is common difference d=... ?

anonymous · Answer

40?

anonymous · Answer

an = 5 + (36 - 1) d
5 + 35 = 40

hartnn · Answer

why did you take d=1 ?

anonymous · Answer

isn't the common difference what I'm looking for?

anonymous · Answer

how does d = 1??

hartnn · Answer

d doesn't equal 1. 
you are looking for a36 
so, you need, a1,n and d
a1=5,n=36, d= ..... ?

anonymous · Answer

I said 40

hartnn · Answer

not actually, " Each row has seven more stones than the prior row"
means common difference = d =7
got this ?

anonymous · Answer

oh, I completely forgot that part. ok so i should plug that in to the formula

hartnn · Answer

yes,
a1= 5, n= 36, d=7
just plug in the formula!

anonymous · Answer

250!!!!!!

hartnn · Answer

yeah, i also get 250 stones in 3th row.

hartnn · Answer

36th ***

anonymous · Answer

omg!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! that wasn't even hard!!!!!!!!!!!!! yayy!!!!!!!

anonymous · Answer

thank you for guiding me!!!!!!

hartnn · Answer

yes, just identify the values of variable and plug in the appropriate equation, thats it!

hartnn · Answer

welcome ^_^

anonymous · Answer

youre the best... i actually feel like i learned!!!!!!

hartnn · Answer

you'll always fell that here. especially when i answer your Q.

hartnn · Answer

*feel

anonymous · Answer

you're so kind, thank you:)

hartnn · Answer

welcome again :)