"Complete the picture graph based on favorite food data collected from children."

Problem Description:

The task involves completing a picture graph based on the data provided in a table. The table shows the number of children who prefer different types of food: Ice-cream, Hamburger, Hotdog, Cake, and Pizza. Each circle in the picture graph represents 3 children.

Given Data:

- Ice-cream: 18 children
- Hamburger: 24 children
- Hotdog: 12 children
- Cake: 15 children
- Pizza: 21 children

Picture Graph Instructions:

Each circle in the graph represents 3 children. We need to determine how many circles to draw for each food item based on the number of children who prefer it.

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Step-by-Step Solution:

#### 1. Ice-cream (18 children)
- Each circle represents 3 children.
- Number of circles needed = Total children / Children per circle
- \( \text{Number of circles} = \frac{18}{3} = 6 \)
- Draw 6 circles.

#### 2. Hamburger (24 children)
- Each circle represents 3 children.
- Number of circles needed = Total children / Children per circle
- \( \text{Number of circles} = \frac{24}{3} = 8 \)
- Draw 8 circles.

#### 3. Hotdog (12 children)
- Each circle represents 3 children.
- Number of circles needed = Total children / Children per circle
- \( \text{Number of circles} = \frac{12}{3} = 4 \)
- Draw 4 circles.

#### 4. Cake (15 children)
- Each circle represents 3 children.
- Number of circles needed = Total children / Children per circle
- \( \text{Number of circles} = \frac{15}{3} = 5 \)
- Draw 5 circles.

#### 5. Pizza (21 children)
- Each circle represents 3 children.
- Number of circles needed = Total children / Children per circle
- \( \text{Number of circles} = \frac{21}{3} = 7 \)
- Draw 7 circles.

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Final Answer:

The completed picture graph should have the following number of circles for each food item:
- Ice-cream: 6 circles
- Hamburger: 8 circles
- Hotdog: 4 circles
- Cake: 5 circles
- Pizza: 7 circles

\[
\boxed{
\begin{array}{c|c}
\text{Food} & \text{Circles} \\
\hline
\text{Ice-cream} & 6 \\
\text{Hamburger} & 8 \\
\text{Hotdog} & 4 \\
\text{Cake} & 5 \\
\text{Pizza} & 7 \\
\end{array}
}
\]