SOMEONE PLEASE HELP!

Question

zehanz · Answer

1.
OK, let's call the common difference c.

month 3 is $150, 
month 4 is $150 + c
month 5 is $150 +2c

But it's also $180.

So solve $150  + 2c = $ 180

zehanz · Answer

2.
Yes, so remember we had formula a(n)=pn+q.
We now have p=15.
To find q, we have to calculate back in time to month 0...

zehanz · Answer

month 0 is ...
month 1 = ...
month 2 is ...
month 3 is $150, 
month 4 is $165
month 5 is $180

zehanz · Answer

2. a(n)=15n+105. 

3. Now set n=12.

zehanz · Answer

I get $285

zehanz · Answer

12a is not right. Look at the formula: a(n)-15n+105. It's just a function.
So to get the amount of the twelfth month, put 12 into this function:

a(12)=15*12+105=285. So that is the amount of the 12th month...

zehanz · Answer

Srry, a(n)=15n+105

zehanz · Answer

4.

Now you have to solve a(n)=500, so:

 15n+105=500

anonymous · Answer

@ZeHanz I got n=26.33 is that right

zehanz · Answer

The calculation is right, but it is not the answer to the question...read it again, please?

anonymous · Answer

ok

anonymous · Answer

im not getting it can u explain

zehanz · Answer

How much money is she depositing the 26th month?

zehanz · Answer

You will have to, because she only deposits money once a month.
If it has to be at least $500, then the 27th month it is!

anonymous · Answer

ohhh Ok!

anonymous · Answer

Thank you so much @ZeHanz !!

zehanz · Answer

You've got me all worn down now...

anonymous · Answer

sorry!:)

zehanz · Answer

Will recover, thanks ;)

anonymous · Answer

thank you!

zehanz · Answer

YW!