Hello!
You first have to look and see if there is an outlier
An outlier is something that is away from the rest of the data
All the numbers are with 1 from each other so there is no outliers
The answer is the first one
Hope this helps!
(-24)+9=-15
(-15)-9=-24
n=-15
Gauss' method for addition relies on the fact that you can 'pair' certain numbers together. Look at the example:
1+2+3+4+5+6+7+8+9+10
We could manually add all these together from left to right but a clever way to think about this is if we add together the ends of the sum (10+1) we get 11. If we then move one in from the ends and add these (2+9) we also get 11. This means that 1+2+...+9+10 is the same as 11+11+...+11+11.
Because each 2 numbers adds to 11 we know the total number of 11's we have to add together is the length of the sum divided by 2. In our case 5 (10 ÷ 2). We need to add 5 lots of 11 to get our answer. This is the same as 11 × 5 which is easily seen to be 55.
(If you add the 10 numbers together on a calculator you'll see 1+2+3+4+5+6+7+8+9+10 = 55) so this method really makes it a lot quicker.
Looking at your sequence, if we pair the ends together we get 401 (400+1) and we multiply this by the length of the sequence divided by 2. In your case, 200 (400 ÷ 2).
So the sum of all the numbers from 1 to 400 must be 401 × 200 = 80,200.
Remember the steps:
1. Pair the ends together and add them
2. Times this number by the length of the sequence halved
Hope this helps.
Answer
Write an expression for the number of pencils Maggie gives to jamil.
To prove
Let us assume that the number of pencils Katie have = x
As given
Katie gives Maggie half of her pencils.
As given
Maggie keeps 5 and gives the rest to jamil.
Thus
Therefore the expression for the number of pencils Maggie gives to jamil are 
.
A. 5
(2,4,5,7,9)
5 is in the middle between 4 and 7.
