Finding a missing part

Worked solution

1. 1

   Identify the known part and the whole.

   $6+\square =10$

   You need enough extra ones to get from six to ten.

2. 2

   Count the extra ones.

   $7, 8, 9, 10$

   Four counts are made after the starting six.

3. 3

   Put four into the blank.

   $6+4=10$

   The completed addition makes the required whole ten.

Worked solution

1. 1

   Separate what stayed from what left.

   $9+\square =14$

   The nine remaining marbles and the removed marbles made the original fourteen.

2. 2

   Count from nine up to fourteen.

   $10, 11, 12, 13, 14$

   Five more marbles are needed to rebuild the original collection.

3. 3

   Check by taking five away.

   $14-5=9$

   Removing five leaves the nine marbles described in the question.