Even Fibonacci Sum

Computer Science Level 3

The Fibonacci series is a sequence of numbers in which each number is the sum of the two previous numbers, starting with 1 and 1.

Example: 1 , 1 , 2 , 3 , 5 , 8 , 13 , 21 , 34 , 55 , 89 , . . . 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...

Assuming the values in the sequence don't exceed four million, what is the sum of the even terms?


The answer is 4613732.

Eric Taylor by Eric Taylor , 21, Canada

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1 solution

Eric Taylor
Jun 18, 2017 
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var previous = 1; // First / Previous value in series
var current = 1; // Second / Current value in series
var next = 0; // Third / Next value in series
var evenSum = 0; // Sum of even numbers in series

while(current < 4000000){
  next = previous + current;

 if(current % 2 == 0) // If current value is even
  evenSum += current;

 previous = current; // "Shift" the values over
 current = next;
}

console.log(evenSum); // Output: 4613732

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