0
1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19 + 21 + 23 + 25 + 27 + 29 + 31 + 33 + 35 + 37 + 39 = 400
1,3,5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39
above are the first 20 odds
If you add the first to the last you get 40
If you add the second to the second from last you get 40
It doesn't matter which numbers you add first so long as you add them all up
there are 10 pairs of numbers totaling 40 so the sum is 400
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Five odd numbers whose sum is 20?
That can't be solved. The sum of five odd numbers will always be an odd number.That can't be solved. The sum of five odd numbers will always be an odd number.That can't be solved. The sum of five odd numbers will always be an odd number.That can't be solved. The sum of five odd numbers will always be an odd number.
If the sum of two numbers is even then the two numbers must be even?
If the sum of two numbers is even, the two numbers are either both even or both odd. A few examples:2 + 4 = 6 (even + even = even)2 + 3 = 5 (even + odd = odd)5 + 2 = 7 (odd + even = odd)7+13 = 20 (odd + odd = even)
How much greater is the sum of the first 20 counting numbers than the sum of the first 10 counting numbers?
It is 155 greater.
How many of the first 30 numbers of the Fibonacci sequence are odd?
20 of them.
What is the sum of the squares of the first 20 natural numbers 1 to 20?
The sum of the first N square numbers is: N*(N+1)*(2N+1)/6 So putting N = 20 gives 2870.
