Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated: 1 00:00:00,120 --> 00:00:03,540 Click on 5.3 adding evens. 2 00:00:05,190 --> 00:00:10,190 The exercise is kind of similar to what Gauss had to do that I showed you in the 3 00:00:11,610 --> 00:00:13,890 last lesson, but in your case, 4 00:00:14,070 --> 00:00:19,070 I want you to calculate the sum of all the even numbers from 1 to 100, 5 00:00:20,310 --> 00:00:24,150 including 1 and 100. So for example, 6 00:00:24,150 --> 00:00:26,730 it might be two plus four plus six plus eight, 7 00:00:26,760 --> 00:00:29,640 and so on and so forth until you get to a hundred. 8 00:00:30,210 --> 00:00:34,260 It's a little bit more complicated than what the ten-year-old had to do. 9 00:00:34,680 --> 00:00:38,280 And the important thing to remember is that there should only be one print 10 00:00:38,280 --> 00:00:40,170 statement in your output. 11 00:00:40,410 --> 00:00:44,940 It should just print the final total and not every step of the calculation. 12 00:00:45,720 --> 00:00:48,270 So have a think about how you might solve this challenge, 13 00:00:48,660 --> 00:00:50,610 pause the video and try to give this a go. 14 00:00:56,450 --> 00:00:56,750 All right. 15 00:00:56,750 --> 00:01:00,590 So there's actually quite a few ways that you could have solved this challenge. 16 00:01:01,160 --> 00:01:01,400 Now, 17 00:01:01,400 --> 00:01:05,480 one of the ways would have been using what we learned from the last lesson and the 18 00:01:05,480 --> 00:01:09,680 ability to create a range function using a different step size. 19 00:01:09,920 --> 00:01:10,753 I'll show you what I mean. 20 00:01:11,150 --> 00:01:16,150 So let's create a full loop where we say for every number in the range between 21 00:01:16,970 --> 00:01:20,030 1 to 100, so that's 101, 22 00:01:20,720 --> 00:01:24,110 then we're going to do something with each number, right? Namely, 23 00:01:24,110 --> 00:01:27,200 we're probably going to create a variable called total 24 00:01:27,590 --> 00:01:32,590 and then we're going to add each of the even numbers together and accumulate it 25 00:01:32,930 --> 00:01:34,190 inside this variable. 26 00:01:34,940 --> 00:01:39,590 Now remember that I mentioned that the range function actually has a third thing 27 00:01:39,590 --> 00:01:42,920 that you can add to it, not just the start and the end, 28 00:01:43,160 --> 00:01:47,210 but also the step size. so we can change the step size to two, 29 00:01:47,660 --> 00:01:52,660 and then now what it's going to do is it's going to go through 1 to 100 and 30 00:01:54,440 --> 00:01:57,230 it's going to increase the step size by two. 31 00:01:58,490 --> 00:02:01,820 So that means if we print this range as it is right now, 32 00:02:01,880 --> 00:02:06,560 it's going to give us one plus two which is three, plus two 33 00:02:06,560 --> 00:02:08,840 which is five and so on and so forth. 34 00:02:09,260 --> 00:02:12,560 But if we change the range to start off from two 35 00:02:12,710 --> 00:02:16,640 which is the first number that we have to start adding in our sequence, and then 36 00:02:16,640 --> 00:02:18,860 increase it by two every single time, 37 00:02:19,130 --> 00:02:23,570 then we end up with a range that includes all of the even numbers up to a 38 00:02:23,570 --> 00:02:26,510 hundred. And I'll show you if I run this code right now. 39 00:02:27,290 --> 00:02:32,000 So the next part is simple. All we have to do is to add the number to 40 00:02:32,000 --> 00:02:35,420 the current total. So total += number. 41 00:02:35,900 --> 00:02:38,570 And then finally outside the for loop, 42 00:02:38,720 --> 00:02:42,230 you can go ahead and print that total. Now, 43 00:02:42,380 --> 00:02:46,490 when I go ahead and run this code now, it's going to give me just the total. 44 00:02:46,850 --> 00:02:50,960 Now remember that the indentation really matters because if I have it like this, 45 00:02:51,260 --> 00:02:54,800 then it's going to give me the total for every step of the calculation, 46 00:02:55,100 --> 00:03:00,100 because it's now included in the for loop and will be executed for as many times 47 00:03:00,910 --> 00:03:05,350 as the for loop runs. But if I remove the indentation, then the 48 00:03:05,350 --> 00:03:08,680 for loop is just this and this is outside of it 49 00:03:08,920 --> 00:03:12,160 so it's only going to give it to me once everything has been done 50 00:03:12,280 --> 00:03:16,360 and I've got the final total. And it's the correct solution. 51 00:03:17,140 --> 00:03:19,870 But you might have also done it in a different way. 52 00:03:20,200 --> 00:03:23,370 You might have said for a number in range, 53 00:03:24,090 --> 00:03:25,860 1 to 101, 54 00:03:26,820 --> 00:03:31,820 and you had some sort of another total, let's call it total2 55 00:03:34,200 --> 00:03:35,460 and started at zero, 56 00:03:35,880 --> 00:03:40,880 and then we say that if the number % 2 is equal to 0, 57 00:03:41,970 --> 00:03:44,490 so if it's even essentially, 58 00:03:44,730 --> 00:03:49,350 then we're going to add this number to the total2. 59 00:03:51,060 --> 00:03:54,480 Finally, outside of the if and outside of the for, 60 00:03:54,750 --> 00:03:58,620 we're going to print the final total. Now, 61 00:03:58,650 --> 00:04:01,140 if I just run the code, then you can see 62 00:04:01,200 --> 00:04:04,350 I get exactly the same number as before. 63 00:04:05,310 --> 00:04:09,240 So if you chose to solve this challenge in either of these ways, 64 00:04:09,270 --> 00:04:11,910 then you've succeeded. They're both right. 65 00:04:12,390 --> 00:04:15,180 And there's probably even other ways that you could solve this as well. 66 00:04:15,480 --> 00:04:18,570 But these two, I suspect will be the most popular approaches. 67 00:04:19,770 --> 00:04:24,150 Now in the next lesson, I've got another coding exercise for you 68 00:04:24,330 --> 00:04:29,160 and it's probably one of the top interview questions that programmers get asked 69 00:04:29,220 --> 00:04:34,020 when they're being interviewed for a job. So head over there and give it a go. 6677