Children who can create reasonable word or story problems for each of these sentences demonstrate that they understand the mean- ings of addition and subtraction with com- mon fractions. 3 8'3\"r 3 __ l 12 1212m2 5 2 7 38+68 8 1 1 5 764iZE > EXERCISE 13.3 Create a problem situation for each of the number sentences in the previous paragraph. If this exercise is difficult for you, why do you think this is so? How does the creation of a word problem for a mathematical sentence provide evidence that a student understands a given operation?