The histogram shows the weights of the children in a Bhopal sports camp. For the class with the most children, what are the class width and the class mark?

A histogram is a bar graph for **grouped** data:

- The $x$-axis shows class intervals (continuous, so bars TOUCH).
- The $y$-axis shows frequency.
- Bar widths are equal (one per class).
- Bar height = frequency of that class.

Difference from a regular bar graph: bar graphs separate distinct categories with gaps; histograms show continuous data with no gaps.