7. A chalkboard has an area of 36 square
   feet. If the chalkboard is 9 feet long, what
   is the height of the chalkboard?

To find the height of the chalkboard, you can use the formula for the area of a rectangle, which is length multiplied by height. Here, you know the area is 36 square feet and the length is 9 feet. So, you can set up the equation:

Area = Length × Height
36 = 9 × Height

To find the height, divide both sides by 9:
Height = 36 / 9 = 4 feet.

So, the height of the chalkboard is 4 feet.

This example highlights a practical application of basic arithmetic in everyday situations. From classrooms to kitchens, knowing how to calculate areas can help in making better use of space! Keeping in mind units of measurement is also key to ensuring accuracy, whether you’re framing a chalkboard or planning a garden.