SOLUTION: What is the sum of all consecutive even integers between 1 and 100 inclusive?

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Question 923653: What is the sum of all consecutive even integers between 1 and 100 inclusive?
Found 3 solutions by josmiceli, MathLover1, MathTherapy:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Suppose you have:
+1+%2B+2+%2B+3+%2B+4+%2B+5+%2B+6+%2B+7+%2B+8+%2B+9+%2B+10+
The sum is +55+
The formula for this is:
+S+=+%28+n%2A%28+n%2B1+%29+%29+%2F+2+
where +n+ is the last number
check:
+55+=+%28+10%2A11+%29+%2F+2+
+55+=+110%2F2+
+55=+55+
OK
Now use it for numbers 1 to 100
+S+=+%28+100%2A101%29%2F2+
+S+=+10100%2F2+
+S+=+5050++

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
Sum of all consecutive integers:
sum=%28n%28n%2B1%29%29%2F2

SUM OF EVEN NUMBERS:
Formula: N%28N%2B1%29
How to Find N+=+%28First_Even+%2B+Last_Even%29%2F2+-1
in your case:
2%2B4%2B6+...+100
find how many even numbers we have from 1 to 100
N+=+%282%2B100%29%2F2-+1+=+50+
go to N%28N%2B1%29 and find a sum of first 50 positive even integers => N%28N%2B1%29=%2850%29%2851%29+=highlight%28+2550%29+


Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!

What is the sum of all consecutive even integers between 1 and 100 inclusive?

The numbers to be summed begin at 2, and end at 100, inclusive
Using the sum of an AP series formula: S%5Bn%5D+=+%28n%2F2%29%282a%5B1%5D+%2B+%28n+-+1%29d%29, where:
S%5Bn%5D is the sum of the numbers in the series
n is the number of numbers in the series
a%5B1%5D is the first term in the series
d is the common difference between each CONSECUTIVE term
Number of consecutive even numbers in the set: %28100+-+2+%2B+2%29%2F2, or 100%2F2, or 50
Therefore, S%5Bn%5D+=+%28n%2F2%29%282a%5B1%5D+%2B+%28n+-+1%29d%29 becomes: S%5Bn%5D+=+%2850%2F2%29%282%282%29+%2B+%2850+-+1%292%29
S%5Bn%5D+=+25%284+%2B+2%2849%29%29
S%5Bn%5D+=+25%284+%2B+98%29
S%5Bn%5D+=+25%28102%29
Sum of series, or highlight_green%28highlight_green%28S%5Bn%5D+=+2550%29%29%29