Here's something fun

OK, I'm going to give you a sequence and I want you to figure out the SUM of all the numbers in that sequence without using a calculator.

34 + 29 + 24 + 19+...+-111

You have to add together all the numbers in the sequence and give me the answer.

For those of you who are baffled right now I'll start you off by giving you the following equation:

Sn = n/2[(2a+(n-1)d]

That should help you.

Remember No calculator, to prove that you didn't use a calculator you have to show your working otherwise you get a big fat 0, haha - I feel so good right now, it's all my maths teacher says.

 

Yikes.
I can appreciate mental flexibility and facility, but I think this is why calculators were invented.
I can, however, figure in my head the sum of integers from 1 to whatever number.

 

You can use pen and paper and also, that equation really makes it simple - Grade D simple.

 

that's arithmetic sequence formula :lol:

 

Un = a + (n - 1)d
-111= 34 + (n - 1)(-5)
= 34 + -5n + 5
-150= -5n
n = 30

Sn = n/2[(2a+(n-1)d]
= 30/2 [2.34+(30-1)(-5)]
= 15[68 + (-145]
= 15[-77]
= -1155

 

I find maths fun

Cool, I'll check your answer once I get home. Chilling in London ATM haha

 

i second this...