Khan Academy Wiki

The topic Teen numbers 3 appears under the Early math Math Mission. This exercise furthers confidence with the naming and size of the teen numbers between ten and twenty.

Types of Problems[]

There are two types of problems in this exercise:

  1. Find the sum and select the quantities: This problem initially has users find the correct sum of two numbers. After doing so, it also asks the user to select all of the options from a multiple select list that correctly represent the same quantity.
    Tn3-1

    Find the sum and select the quantities

  2. How many and how many until: This problem has a person that has collected more than ten of some object. The question asks the user to identify how many the person in the problem has, and how many more they will need to reach twenty.
    Tn3-2

    How many and how many until

Strategies[]

Addition up to copies of ten is all that is required for success on this exercise. A model, such as fingers, can be used to assist.

  1. On the Find the sum and select the quantities problem there will always be three options selected from the multiple select list. The one left out is always the one with a "1" instead of a "10."
  2. To increase speed, it is recommended to perform the multiple select first and then write the answer. Then the "enter" button can be pushed to submit the solution.
  3. On How many and how many until the answer to the first question is a number between 11 and 20, so start typing 1 and then read the problem for the number left over. The second answer is the single digit number that adds to the first answer to make twenty so finding one answer will lead to the other by connecting 1-9, 2-8, 3-7, 4-6 and 5 with itself.

Real-life Applications[]

  1. Knowing how to count is essential for learning algebra and the higher maths, and counting is used for almost everything humans do.