help me please!!! i need to submit it on this friday.. :(

[tinifazlen]

1. find the sum of all integers between 200 and 400 which are multiples of 3 but not 5.

2.if the sum of the first 4 terms of an AP is x ,the sum of the first 8 terms is y and the sum of the first 12 terms is z,show that 3x+z=3y.


3.if lgx,lg(x+2) and lg (x+16) are three consecutive terms of an AP. find the value of x.


4.find the sum of the series 20^2-19^2+18^2-17^2+16^2-15^2 +...+2^2-1^2 :shock:

 

[Deleted member 4993]

1. find the sum of all integers between 200 and 400 which are multiples of 3 but not 5.

2.if the sum of the first 4 terms of an AP is x ,the sum of the first 8 terms is y and the sum of the first 12 terms is z,show that 3x+z=3y.


3.if lgx,lg(x+2) and lg (x+16) are three consecutive terms of an AP. find the value of x.


4.find the sum of the series 20^2-19^2+18^2-17^2+16^2-15^2 +...+2^2-1^2 :shock:

Hint:

Problem 1 →

howmany numbers between 200 and 400 are divisible by 3?

how many numbers between 200 and 400 are divisible by 5?

how many numbers between 200 and 400 are not divisible by 5?

Now what....

Please share your work with us.

You need to read the rules of this forum. Please read the post titled "Read before Posting" at the following URL:

http://www.freemathhelp.com/forum/th...217#post322217

We can help - we only help after you have shown your work - or ask a specific question (e.g. "are these correct?")