Khan Academy Wiki

The Finding area by multiplying exercise appears under the 3rd grade (U.S.) Math Mission, 4th grade (U.S.) Math Mission. This exercise tries to connect multiplication (and arithmetic concept) with area (a geometric concept) in a meaningful way.

Types of Problems[]

There are two types of problems in this exercise:

  1. Realize multiply is area: This problem has an array of squares drawn. The user is to fill in three numbers and one pop-up menu to complete the problem.
    Aremult1

    Realize multiply is area

  2. Fill in information: This problem has an area problem illustrated as a multiplication problem. The user is tasked to fill in the five correct answers, including rows and columns twice and the answer for the area.
    Aremult2

    Fill in information

Strategies[]

This exercise is medium to get accuracy badges because of the careful reading that is necessary to make sure user is comparing rows and columns correctly. This necessary careful reading makes speed badges hard.

  1. On the first problem type, the drop down solution is always multiply which is found by pressing down three times in the drop down menu.
  2. On the second problem type the order of the questions (width vs. length) can change in the second set of entries. This is very good as length and width can be viewed as somewhat ambiguous.

Real-life Applications[]

  1. Area and perimeter are used for building a swimming pool. The owner of the pool wants to maximize the area within constraints of property and minimize the amount of digging and concrete, etc. that goes into the project. Yet the perimeter also defines length that is used for swimming races.