If we join the mid points of the upper horizontal sides of each rectangle of a histogram by straight lines, what is the figure so obtained known as?

Options

A. Frequency curve
B. Frequency polygon
C. Ogive (gt)
D. Ogive (lt)

Explanation

To solve the question, we need to understand the concept of a histogram and the procedure for creating a frequency polygon from it.

### Step-by-Step Solution:

1. **Understanding the Histogram**: A histogram is a graphical representation of the distribution of numerical data. It consists of rectangles (bars) where the height of each rectangle represents the frequency of data within a certain range (class interval).

2. **Identifying Midpoints**: For each rectangle in the histogram, we need to find the midpoints of the upper horizontal sides. The midpoint of a rectangle is simply the average of the two endpoints of the top side of the rectangle.

3. **Joining the Midpoints**: Once we have identified the midpoints of the upper sides of all rectangles, we will connect these midpoints with straight lines. This means we will draw a line from the midpoint of the first rectangle to the midpoint of the second rectangle, and so on, until we reach the last rectangle.

4. **Resulting Figure**: The figure formed by connecting these midpoints is known as a frequency polygon. This polygon visually represents the same data as the histogram but in a different form.

5. **Conclusion**: Therefore, the figure obtained by joining the midpoints of the upper horizontal sides of each rectangle of a histogram by straight lines is called a **frequency polygon**.