Join+Start+Unknown

=__Join Start Unknown __=

Connie had some marbles. Juan have gave her 5 more marbles. Now she has 13 marbles. How many marbles did Connie have to start with?

__Strategy__ : Trial and Error

Number Sentence : ? + 5 = 13

The student begins with an unknown amount of counters and figures out through the counting process that he/she may have too many or not enough. They may have to count it out a few times to get the correct amount needed. He or she will then adjust the initial pile of counters to fit the amount 13 (given the the problem as the sum). media type="file" key="Movie on 2010-11-01 at 12.48.mov" width="300" height="300"

__Strategy__ : By Separation

Number Sentence: 5 + ? = 13

The student knows he/she will begin with 5 knowing the sum is 13. He/she then uses 5 as the initial point of counting and then counts to 13. They discover then that it takes 8 counters to reach the sum of 13.

media type="file" key="Movie on 2010-11-01 at 12.57.mov" width="300" height="300"

__Strategy__ : Counting Down

Number Sentence : 13 - ? = 5

The student begins counting from 13 as the initial starting point and then counts down until he/she reaches 5.

__Strategy__ : Counting Up

Number Sentence : 5 + ? = 13

The student begins counting from 5 as the initial starting point and then counts up until he/she reaches 13.