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.
Using the triangle inequality theorem, we can figure this out.
2- Yes
3- No
4- No
5- Yes
6- Yes
Answer:
$1136.60
Step-by-step explanation:
The formula for exponential growth is f(x) = a(1 + r)^x where a is the initial value, r is the growth rate, and x is the number of time intervals.
We know that Mr. Paris starts with an $1800 initial value, so we can substitute that into the equation:
f(x)=1800(1 + r)^x
We also know the time intervals is 6 months. So that can be substituted as well:
f(x)=1800(1 + r)^6
They told you that the growth rate is 8.5%, which is 0.085 of 1.
f(x)=1800(1 + 0.085)^6
Add the 2 values in the parentheses and you get 1.085
f(x)=1800(1.085)^6
Now solve.
Order of operations requires you to raise 1.085 to the 6th power before multiplying by 1800. So then you have this:
1800(1.63146751) = 2936.64152. That rounds to 2936.60
So $2936.60 is the total amount of money in the bank account, but were looking for the interest earned, which is the difference between the end value and the initial value.
$2936.60 - $1800 = $1136.60
Answer:
£191.36
Step-by-step explanation:
Sum the parts of the ratio, 1 + 4 = 5 parts
Divide 320 by 5 to find the value of one part of the ratio.
320 ÷ 5 = 64 ← value of 1 part of the ratio , thus
4 parts = 4 × 64 = 256
Thus he bought 64 first class and 256 second class.
Cost = (64 × £0.67) + (256 × £0.58)
= £42.88 + 148.48
= £191.36