Can anyone explain this to me ?

[nODZ]

So i'm doing stef's css course right now , and i love it , but there is one question that makes no sense to me. In chapter 4 The Box Model , lesson 7  calculate width  / question 3 there is a question that  goes like this :   Please update the margin on this div , so that it will fit into 400px. the code is  <div style="width: 300px; padding: 10px; border: 0px; margin:">. So on margin i added 15px , the way i see it width is 300px + padding 40 (10x4) so i thought we need 60px (4x15) to make it 400px , but the answer says 40px is the correct answer ,  dont get why?

Edited November 7, 2018 by nODZ

[Andrea]

The pudding is inside the width, so you would add a right and left margin of 50px each.

[Andrea]

...also,  even if you needed to include tja padding, you would only consider the right and left, not top and bottom. And I jut see the answer should be 40.....  why is that? (It’s been a while for me, what am I overlooking?)

[nODZ]

okay I see what I did wrong, so it's the width that he is looking,(i thought total) !so 300 + 10 padding on left and right = 320, so we add the margin of 40px to left and right (total 80px). 320+80=400width

tnx for reply btw