The importance of place value
I always start the school year with number sense. Why? Because it gives me a good indication of each student’s comfort with numbers. Number sense is the one strand that is always interwoven into other strands in mathematics. It is also the most telling predictor of a child’s success in math. If they have a good number sense – they can work flexibly and easily with numbers in most situations. If they don’t, I will have an idea of how to construct the rest of my lessons so that those students finish the year feeling more confident with numbers.
So what concept do most teachers start with? Place value. Place value is one of the hardest yet most important skills for primary students to master.
“Place value is the understanding that the same numeral represents different amounts depending on which position it is in.” (Charlesworth, 2012)
“The most critical period in this development occurs in grades pre-K to 2” (Van de Walle, 2014).
The understanding of place value follows this progression:
Level 1: Initial concept of 10 (see 10 as ten units).
Level 2: Intermediate concept of 10 (see 10 as a unit of ten ones but rely on
physical or mental models to do so)
Level 3: Facile concept of 10 (easily work with units of 10 without the use of
Place value development carries on through the elementary years by increasing the place value to build bigger numbers. But it is more than just knowing how to read big numbers; it is crucial to the learning of trading rules that underlie whole number operations. As a result, it is the most important building block for number sense.
Sadly, all too many children have a rote understanding of place value without truly understanding what different place values actually mean. They are not able to go back and forth between equivalent representations of the same number (i.e. 31 could be three groups of 10 and one 1or it could be 2 groups of 10 and 11 ones).
Introducing place value
Rory has just started kindergarten (my baby!!!!) and he has no understanding of place value (and nor should he!). He does have a good understanding of conservation of number though, meaning he understands that different arrangements of counters still mean the same number. To introduce him to place value, I did the following:
1) I asked him which was larger 63 or 36 to see if he has any understanding of what he’s counting or place value. He didn’t. Interviewing children is a great way to gauge their ability and find out what they’re thinking and why.
2) I gave him a bunch of unifix cubes (a great model to start with!) and asked him to count as high as he could. This is a great test for cardinality and one-to-one correspondence. Both he and I were surprised that he made it to 39 without any assistance!
3) I asked him to now group the cubes into groups of 10 which he did easily. He quickly noticed if a group of 10 was incomplete (the benefit of a proportional model!).
4) We finished by noticing that the number of groups of 10 corresponds to the place value in the number. This went way over his head, but I felt better for saying it!
If this were a classroom lesson, I would complete it with a comparison of one ten tower to one cube and engage the students in a discussion of what they notice.
Do’s and Don’ts for Teaching Place Value
So how do you teach something this important? Here are some do’s and don’ts
- DO use proportional manipulatives (the hundreds should be bigger than the tens which should be bigger than the ones)
- DO use many different manipulatives so the child doesn’t think PV can only be represented with one type (i.e. base 10 blocks, unifix cubes, paperclips, counters)
- DO integrate PV teaching with estimation and computation tasks
- DO integrate PV teaching with measurement tasks (and use different units to measure!)
- DO work on PV skills throughout the school year (not just in September!)
- DO question and assess students constantly to be sure they are really understanding the concepts and not just answering in a rote manner
- DO engage students in composing and decomposing #’s in a wide variety of ways
- DO allow children to invent their own computation strategies
- DON’T give worksheets which encourage a rote understanding not a concrete understanding (i.e 6 tens and 4 ones is 64 in all.)
- DON’T teach PV abstractly, tie it to a manipulative
- DON’T rush into operations involving regrouping tasks i.e. borrowing and carrying (mental math rarely involves regrouping as a strategy) and you run the risk of students not conceptualizing place value
- DON’T start computation with numbers that don’t require regrouping (i.e. 23 +45); otherwise students will think that 56 + 35 = 811
- DON’T rely on one type of manipulative (i.e. base 10 blocks) or children will memorize that a rod is ten and a small cube is one without actually understanding how many ones make a rod
- DON’T teach PV in isolation, make it rich by integrating it with other subjects (see the link below for suggestions)
A true understanding of place value doesn’t usually happen until the concrete stage of development (7-8 years old), but it doesn’t mean you shouldn’t provide lots of opportunities for its development. What can you do? COUNT EVERYTHING!!!!
Want more suggestions? Click here!