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CSSmarkup~10 mins

Relative units in CSS - Interactive Code Practice

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Practice - 5 Tasks
Answer the questions below
1fill in blank
easy

Complete the code to set the font size to 2 times the root element's font size.

CSS
p { font-size: 2[1]; }
Drag options to blanks, or click blank then click option'
Arem
Bpx
Cem
D%
Attempts:
3 left
💡 Hint
Common Mistakes
Using px which is absolute, not relative.
Confusing em with rem.
2fill in blank
medium

Complete the code to set the margin to 5% of the parent element's width.

CSS
div { margin: [1]; }
Drag options to blanks, or click blank then click option'
A5px
B5rem
C5%
D5em
Attempts:
3 left
💡 Hint
Common Mistakes
Using px which is fixed size.
Using rem which relates to root font size, not parent width.
3fill in blank
hard

Fix the error in the code to set padding relative to the current element's font size.

CSS
section { padding: 1[1]; }
Drag options to blanks, or click blank then click option'
Apx
Bem
Crem
D%
Attempts:
3 left
💡 Hint
Common Mistakes
Using px which is fixed size.
Using rem which relates to root, not current element.
4fill in blank
hard

Fill both blanks to set the width to 50% of the viewport width and height to 10% of the viewport height.

CSS
div { width: 50[1]; height: 10[2]; }
Drag options to blanks, or click blank then click option'
Avw
Bvh
C%
Dem
Attempts:
3 left
💡 Hint
Common Mistakes
Using % which relates to parent, not viewport.
Using em which relates to font size.
5fill in blank
hard

Fill all three blanks to create a responsive font size: 1.5 times the root font size, with a margin of 2% and padding of 1em.

CSS
p { font-size: 1.5[1]; margin: 2[2]; padding: 1[3]; }
Drag options to blanks, or click blank then click option'
Arem
B%
Cem
Dpx
Attempts:
3 left
💡 Hint
Common Mistakes
Using px for font size or margin which is not responsive.
Confusing em and rem units.

Practice

(1/5)
1. Which CSS unit is relative to the root element's font size?
easy
A. em
B. rem
C. px
D. vw

Solution

  1. Step 1: Understand root-relative units

    The rem unit always refers to the font size set on the root <html> element.

  2. Step 2: Compare with other units

    em is relative to the parent element's font size, px is fixed pixels, and vw is relative to viewport width.

  3. Final Answer:

    rem -> Option B

  4. Quick Check:

    Root font size = rem [OK]
Hint: Root font size uses rem, not em or px [OK]
Common Mistakes:
  • Confusing em with rem
  • Thinking px is relative
  • Mixing viewport units with font units
2. Which of the following is the correct syntax to set a font size to 2 times the parent element's font size?
easy
A. font-size: 2vw;
B. font-size: 2rem;
C. font-size: 2px;
D. font-size: 2em;

Solution

  1. Step 1: Identify the unit for parent-relative size

    em units scale relative to the parent element's font size.

  2. Step 2: Check other options

    rem is root-relative, px is fixed, and vw is viewport width relative.

  3. Final Answer:

    font-size: 2em; -> Option D

  4. Quick Check:

    Parent-relative font size = em [OK]
Hint: Use em for parent-relative sizes, rem for root-relative [OK]
Common Mistakes:
  • Using rem instead of em for parent size
  • Using px which is fixed size
  • Confusing vw with font size units
3. Given the CSS below, what will be the width of the <div> if the viewport width is 1000px?
div {
  width: 50vw;
}
medium
A. Depends on parent width
B. 50px
C. 500px
D. 1000px

Solution

  1. Step 1: Understand vw unit

    1vw equals 1% of the viewport width. So 50vw is 50% of viewport width.

  2. Step 2: Calculate width

    Viewport width is 1000px, so 50vw = 50% of 1000px = 500px.

  3. Final Answer:

    500px -> Option C

  4. Quick Check:

    50vw = 50% viewport width = 500px [OK]
Hint: vw is % of viewport width, multiply by viewport size [OK]
Common Mistakes:
  • Thinking vw depends on parent width
  • Confusing vw with px
  • Calculating 50vw as 50px
4. What is wrong with this CSS if the goal is to make the font size 1.5 times the parent font size?
p {
  font-size: 1.5rem;
}
medium
A. rem is root-relative, not parent-relative
B. 1.5rem is invalid syntax
C. font-size cannot use rem units
D. Should use px instead of rem

Solution

  1. Step 1: Identify unit behavior

    rem units are relative to the root font size, not the parent element.

  2. Step 2: Match goal with unit

    To scale relative to the parent font size, em should be used instead of rem.

  3. Final Answer:

    rem is root-relative, not parent-relative -> Option A

  4. Quick Check:

    Parent-relative size needs em, not rem [OK]
Hint: Use em for parent-relative font size, not rem [OK]
Common Mistakes:
  • Thinking rem scales with parent
  • Believing 1.5rem is invalid syntax
  • Using px for scalable font sizes
5. You want a button width to be 30% of the viewport width but never smaller than 200px. Which CSS snippet correctly uses relative units and a minimum width?
hard
A. button { width: 30vw; min-width: 200px; }
B. button { width: 30%; min-width: 200vw; }
C. button { width: 30rem; min-width: 200px; }
D. button { width: 30em; min-width: 200%; }

Solution

  1. Step 1: Understand width units

    30vw means 30% of viewport width, which matches the requirement.

  2. Step 2: Check minimum width

    min-width: 200px ensures the button never shrinks below 200 pixels.

  3. Step 3: Verify other options

    Other options fail: 30rem is root font-relative; 30% with min-width: 200vw uses parent-relative width and huge min-width; 30em with min-width: 200% uses font-relative and parent-relative units incorrectly.

  4. Final Answer:

    button { width: 30vw; min-width: 200px; } -> Option A

  5. Quick Check:

    30vw + min-width: 200px [OK]
Hint: Use vw for viewport %, min-width in px for fixed minimum [OK]
Common Mistakes:
  • Using % for viewport width instead of vw
  • Setting min-width in vw or % incorrectly
  • Confusing rem/em with viewport units