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Click on 5.3 adding evens.

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The exercise is kind of similar to what Gauss had to do that I showed you in the

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last lesson, but in your case,

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I want you to calculate the sum of all the even numbers from 1 to 100,

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including 1 and 100. So for example,

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it might be two plus four plus six plus eight,

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and so on and so forth until you get to a hundred.

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It's a little bit more complicated than what the ten-year-old had to do.

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And the important thing to remember is that there should only be one print

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statement in your output.

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It should just print the final total and not every step of the calculation.

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So have a think about how you might solve this challenge,

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pause the video and try to give this a go.

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All right.

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So there's actually quite a few ways that you could have solved this challenge.

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Now,

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one of the ways would have been using what we learned from the last lesson and the

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ability to create a range function using a different step size.

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I'll show you what I mean.

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So let's create a full loop where we say for every number in the range between

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1 to 100, so that's 101,

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then we're going to do something with each number, right? Namely,

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we're probably going to create a variable called total

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and then we're going to add each of the even numbers together and accumulate it

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inside this variable.

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Now remember that I mentioned that the range function actually has a third thing

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that you can add to it, not just the start and the end,

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but also the step size. so we can change the step size to two,

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and then now what it's going to do is it's going to go through 1 to 100 and

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it's going to increase the step size by two.

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So that means if we print this range as it is right now,

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it's going to give us one plus two which is three, plus two

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which is five and so on and so forth.

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But if we change the range to start off from two

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which is the first number that we have to start adding in our sequence, and then

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increase it by two every single time,

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then we end up with a range that includes all of the even numbers up to a

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hundred. And I'll show you if I run this code right now.

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So the next part is simple. All we have to do is to add the number to

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the current total. So total += number.

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And then finally outside the for loop,

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you can go ahead and print that total. Now,

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when I go ahead and run this code now, it's going to give me just the total.

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Now remember that the indentation really matters because if I have it like this,

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then it's going to give me the total for every step of the calculation,

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because it's now included in the for loop and will be executed for as many times

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as the for loop runs. But if I remove the indentation, then the

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for loop is just this and this is outside of it

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so it's only going to give it to me once everything has been done

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and I've got the final total. And it's the correct solution.

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But you might have also done it in a different way.

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You might have said for a number in range,

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1 to 101,

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and you had some sort of another total, let's call it total2

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and started at zero,

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and then we say that if the number % 2 is equal to 0,

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so if it's even essentially,

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then we're going to add this number to the total2.

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Finally, outside of the if and outside of the for,

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we're going to print the final total. Now,

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if I just run the code, then you can see

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I get exactly the same number as before.

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So if you chose to solve this challenge in either of these ways,

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then you've succeeded. They're both right.

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And there's probably even other ways that you could solve this as well.

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But these two, I suspect will be the most popular approaches.

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Now in the next lesson, I've got another coding exercise for you

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and it's probably one of the top interview questions that programmers get asked

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when they're being interviewed for a job. So head over there and give it a go.