Math and Arithmetic
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# What is the sum of the first 9 odd numbers?

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###### 2014-07-30 10:52:07

The sum of the first nine odd numbers is 81.

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## Related Questions

The first three odd numbers are 1, 3, and 5. Their sum is 1 + 3 + 5 = 9.

9801 * The sum of the first two odd numbers (1+3) is 4, or 22 * The sum of the first three odd numbers (1+3+5) is 9, or 32 * The sum of the first four odd numbers (1+3+5+7) is 16, or 42 * ...and so on So the sum of the first 99 odd numbers, using the pattern above, would be 992 or 9801.

The sum of 9 odd numbers must be odd and so cannot be an number.

the sum of the first three numbers is 1 + 3+5= 9

You can work this out by realizing that the sum of the first x odd numbers is equal to x2.Consider the following examples:The first three odd numbers: 1 + 3 + 5 = 9The first five odd numbers: 1 + 3 + 5 + 7 + 9 = 25The first ten odd numbers: 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 = 100In each case, the number of odds you're adding together is the square root of their sum. This means that the first 1500 consecutive odd numbers have a sum of 15002, which equals 2250000, or two and a quarter million.

You cannot. The sum of 9 odd numbers must be odd.

Answer is 4000000: The sum of the first N odd numbers is N^2. Look at 1,3,5 for example. There are 3 numbers and the sum is 9 which is 3^2. Add 7 and the sum is 16 which is 4^2. So the of the first 2000 consecutive odd numbers is 2000^2 Note 2000 is 2(10^3). When we square that it is 4x10^6=4000000

Not possible ! If you add an odd number of odd numbers together, the result will ALWAYS be odd !

1, 3, 5, 7, 9, 11 are six consecutive odd numbers whose sum is 36

An odd number of odd numbers can't add up to an even number.

Let's talk this out and see if we can work it out. The sum of the first N odd integers means, 1+3+5+7+9+11+... Where N is how many odd numbers we're adding. Let's choose numbers for N, and see if we can find a pattern. N=1 --&gt; 1 (sum of the first odd integer) N=2 --&gt; 1 + 3 = 4 (sum of the first 2 odd integers) N=3 --&gt; 1 + 3 + 5 = 9 (sum of the first 3 odd integers) N=4 --&gt; 1 + 3 + 5 + 7 = 16 Do you notice a pattern yet? Take a look at when N = 2, what is the sum? That's right, 4! and when N = 3... the sum is 9. N = 4 the sum is 16.... I see a pattern, do you? Answer: If you don't, you'll notice that the sum of the first N odd integers is always = N2

If you include 8 and 18 that is 11 numbers and their sum is 143 which is odd ---- Explanations (by the way, it is really not all the numbers between 8 and 18, it is just all the integers. There is an infinite number of numbers between 8 and 18, think of just 8, 8.1, 8.11, 8.111, 8.1111 etc) Here are some other fun ways to do this: One way to do it, of course is just to add 8+ 9 10 11 12 13 14 15 16 17 18 Before you add them all, consider just adding the last column, and looking at the ones column of that number. 8+9+0+1+2+....+8 that number is 53 so the sum is odd. If that numbers is even then the number is even OR Looking at just the odd numbers. The sum of even numbers is always even. An odd number and an even number is an odd number. So if the sum of the odd numbers is even then the last column will be an odd number and the total sum will be odd. The sum of odd numbers is even when there is an even number of them. Look at 2 odd numbers. (ie 3+3 =6, this is two odd numbers and their sum is even) 9,11,13,15,17 are even and there are 5 of them. This is an odd number of odd so the sum is odd. Now we know the sum of the odds and the evens is odd so the total of the last column must be odd and therefore the sum is odd. Another way is to see that the sum of the first n numbers is n(n+1)/2 We can add the sum of the first 18 numbers then subtract the sum of the first 7 numbers and what is left is the sum of the numbers 8 to 18. So in this case we have 18x19/2-8x9/2 which is (18x19-7x8)/2 this simplifies by first dividing the 18 and the 8 by 2 so we have 9x19-4x7= 171-28=143 OR What if we match up and add the 8 and the 18, the 9 and the 17, the 10 and the 16, the 11 and the 15, the 12 and the 14 and you have 13 left. This is the idea behind the formula for the first n numbers. That is 26x5+13=143

Because the sum of the first N odd numbers is always N squared. Look at 5, 7, and 9. This is 5+7+9 = (1 + 3 + 5 + 7 + 9)-(1+3)= 25-4 =5^2 - 2^2

There is no way without playing silly games. Each of the numbers in the list is odd. The sum of five odd numbers must be odd and therefore, cannot be 50. There is no way without playing silly games. Each of the numbers in the list is odd. The sum of five odd numbers must be odd and therefore, cannot be 50. There is no way without playing silly games. Each of the numbers in the list is odd. The sum of five odd numbers must be odd and therefore, cannot be 50. There is no way without playing silly games. Each of the numbers in the list is odd. The sum of five odd numbers must be odd and therefore, cannot be 50.

The sum of the first three prime numbers that end with a 9 (19,29,59) is 107

they can't. 7 odd DIGITS can, but you have to use a two-digit number eg: 15 + 9 + 9 + 9 + 9 + 9 = 60

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