I am not sure when I learned how to write numbers in expanded notation, but I am certain it was not in 3rd grade. Students now are expected to learn how to write numbers in expanded notation as early as 3rd grade here in Texas and I am sure that applies to other states as well. But why? It is part of a push to help students understand the relationships between places and digits in our base ten number system. It can seem difficult at times, but with hands on activities and a lot of practice, your students can master expanded notation.
One method I find to be very effective is using play money:
Give your students a number. Guide them to use their play value money to model the number.
Then ask them “Ask “How many hundred thousands?” Tell “Expanded notation shows the number in each place times the value of the place, so 3 hundred thousands is 3 x 100,000.”
Continue questioning and guiding students to use play money to help them write the numbers.
You can download my play money for FREE by clicking the picture below.