The number choices in the Compare problems in this lesson encourage students to use methods based on place value to find the unknown value. Students may look for ways to compose a ten or subtract multiples of ten when finding unknown values within 100. Students will subtract numbers other than multiples of ten within 100 in future lessons. Encourage students to use a tape diagram to make sense of the problem if it is helpful.

What connections did students make between story problem contexts and the placement of the question mark in tape diagrams?  How are students using tape diagrams to make sense of Compare problems?