Column sizing (col-1 through col-12) in Bootsrap - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Bootstrap column sizing

In Bootstrap's grid system, what does the class col-6 mean for a column inside a row?

A The column takes up half the width of the row (6 out of 12 parts).

B The column takes up 6 pixels width.

C The column is hidden on screens smaller than 6 inches.

D The column takes up 6% of the row width.

💡 Hint

Bootstrap grid divides the row into 12 equal parts.

In Bootstrap, the grid system divides the row into 12 equal parts. The class col-6 means the column uses 6 of those 12 parts, so half the row width.

📝 Syntax

intermediate

Which Bootstrap class creates a column that is one quarter width?

You want a column that takes exactly 1/4 of the row width. Which class should you use?

A col-6

B col-4

C col-3

D col-9

💡 Hint

Remember the grid is divided into 12 parts.

Since 12 divided by 4 is 3, col-3 means the column takes 3 out of 12 parts, which is one quarter of the row.

❓ rendering

advanced

Visual layout with mixed column sizes

Given this HTML snippet, what will be the visual width distribution of the columns inside the row?

<div class="row">
  <div class="col-4">A</div>
  <div class="col-8">B</div>
</div>

A Column A takes 1/3 width, Column B takes 2/3 width.

B Column A takes 4% width, Column B takes 8% width.

C Both columns take equal width.

D Column A takes 4/12 width, Column B takes 8/12 width.

💡 Hint

Bootstrap columns add up to 12 parts per row.

The col-4 class means 4 parts out of 12, and col-8 means 8 parts out of 12. So column A is 4/12 and column B is 8/12 of the row width.

❓ selector

advanced

Selecting columns with specific width in CSS

You want to write a CSS rule that targets only Bootstrap columns that take exactly 3 parts of the grid (col-3). Which selector is correct?

A .col-3

B [class^="col-"]

C .col-3, .col-6

D .col-3 > *

💡 Hint

Bootstrap column classes are named col-1, col-2, ..., col-12.

The class .col-3 targets exactly the columns with class col-3. The other selectors are either too broad or incorrect.

❓ accessibility

expert

Ensuring accessible layout with Bootstrap columns

When using Bootstrap column classes like col-1 through col-12, what is the best practice to ensure screen readers understand the layout order correctly?

A Add aria-hidden="true" to all columns except the first.

B Use semantic HTML elements and avoid changing visual order with CSS only.

C Use tabindex="-1" on columns to skip them in keyboard navigation.

D Use inline styles to reorder columns visually without changing HTML order.

💡 Hint

Screen readers read content in the order it appears in the HTML.

Using semantic HTML and keeping the logical order in the markup ensures screen readers read content in the correct sequence. Visual reordering with CSS can confuse assistive technologies.

Practice

1. What does the Bootstrap class col-6 mean in a grid layout?

easy

A. The column takes up half the width of the row (6 out of 12 parts).

B. The column takes up 6 pixels width.

C. The column is hidden on screens smaller than 6 inches.

D. The column has 6 columns inside it.

Solution

1. Step 1: Understand Bootstrap grid system

   Bootstrap divides a row into 12 equal parts for layout.

2. Step 2: Interpret col-6

   The class col-6 means the column uses 6 of those 12 parts, which is half the row width.

3. Final Answer:

   The column takes up half the width of the row (6 out of 12 parts). -> Option A

4. Quick Check:

   col-6 means 6/12 width = half [OK]

Hint: Remember: col-# means # out of 12 parts width [OK]

Common Mistakes:

• Thinking col-6 means 6 pixels wide
• Confusing col-6 with number of columns inside
• Assuming col-6 hides the column on small screens

2. Which of the following is the correct way to create a column that takes one quarter of the row width using Bootstrap classes?

easy

A. col-3

B. col-4

C. col-6

D. col-9

Solution

1. Step 1: Calculate quarter width in 12 parts

   One quarter of 12 parts is 12 ÷ 4 = 3 parts.

2. Step 2: Match with Bootstrap class

   The class col-3 means 3 parts width, which is one quarter.

3. Final Answer:

   <code>col-3</code> -> Option A

4. Quick Check:

   3 parts = 1/4 width [OK]

Hint: Divide 12 by desired fraction to find col-# [OK]

Common Mistakes:

• Choosing col-4 which is one third, not quarter
• Confusing col-6 as quarter width
• Picking col-9 which is three quarters

3. Given this HTML snippet:

<div class='row'>
  <div class='col-4'>A</div>
  <div class='col-8'>B</div>
</div>

How will the columns appear on a large screen?

medium

A. Column A takes 4/12 width, Column B takes 8/12 width stacked vertically.

B. Column A and B stack vertically, each full width.

C. Column A takes 1/3 width, Column B takes 2/3 width side by side.

D. Column A takes 8/12 width, Column B takes 4/12 width side by side.

Solution

1. Step 1: Understand col-4 and col-8 widths

   col-4 means 4 parts out of 12 (1/3), col-8 means 8 parts out of 12 (2/3).

2. Step 2: Check layout behavior in Bootstrap

   Columns inside a row appear side by side if total is 12 or less.

3. Final Answer:

   Column A takes 1/3 width, Column B takes 2/3 width side by side. -> Option C

4. Quick Check:

   4 + 8 = 12 parts, side by side [OK]

Hint: Sum col-# classes; if 12 or less, columns sit side by side [OK]

Common Mistakes:

• Thinking columns stack vertically by default
• Mixing up col-4 and col-8 widths
• Assuming col-4 means 1/4 width

4. What is wrong with this Bootstrap column layout?

<div class='row'>
  <div class='col-5'>X</div>
  <div class='col-8'>Y</div>
</div>

medium

A. The classes col-5 and col-8 are invalid in Bootstrap.

B. The columns add up to more than 12, causing layout issues.

C. The columns will stack vertically because col-5 is less than col-6.

D. The row class is missing, so columns won't align.

Solution

1. Step 1: Add column widths

   col-5 means 5 parts, col-8 means 8 parts; total is 5 + 8 = 13 parts.

2. Step 2: Check Bootstrap grid rules

   Columns in a row should add up to 12 or less for proper layout; more than 12 breaks layout.

3. Final Answer:

   The columns add up to more than 12, causing layout issues. -> Option B

4. Quick Check:

   5 + 8 = 13 > 12 breaks layout [OK]

Hint: Sum col-# classes; must be ≤ 12 for correct layout [OK]

Common Mistakes:

• Thinking col-5 or col-8 are invalid classes
• Assuming columns stack because of size difference
• Ignoring total width exceeding 12

5. You want to create a responsive layout with three columns where:
- The first column is 3 parts wide
- The second column is twice as wide as the first
- The third column fills the remaining space
Which Bootstrap classes should you use?

hard

A. col-3, col-5, col-4

B. col-3, col-6, col-4

C. col-2, col-4, col-6

D. col-3, col-6, col-3

Solution

1. Step 1: Assign widths based on conditions

   First column = 3 parts; second column = twice first = 6 parts.

2. Step 2: Calculate remaining space for third column

   Total so far: 3 + 6 = 9 parts; remaining = 12 - 9 = 3 parts.

3. Step 3: Match with Bootstrap classes

   Use col-3, col-6, and col-3 for the three columns respectively.

4. Final Answer:

   <code>col-3</code>, <code>col-6</code>, <code>col-3</code> -> Option D

5. Quick Check:

   3 + 6 + 3 = 12 parts total [OK]

Hint: Double first col width, subtract sum from 12 for last [OK]

Common Mistakes:

• Choosing widths that sum over 12
• Not doubling the first column width correctly
• Assigning third column more than remaining space