Free until March 1, 2016. Practice representing 2-digit numbers 10-99. Designed specifically for use in K-1 classrooms. Drag 10s and 1s blocks one at a time to the work area to represent the target number displayed. OR, drag the Blocks into place and then identify the number. Feedback is provided at any time by tapping the “checkmark” button at the top of the screen. Options include selecting a specific target number or letting the app randomly select a target from the range you select. Common Core: Kindergarten CCSS.MATH.CONTENT.K.NBT.A.1 Work with numbers 11-19 to gain foundations for place value. Common Core: 1st Grade CCSS.MATH.CONTENT.1.NBT.B.2 Understand place value. Understand that the two digits of a two-digit number represent amounts of tens and ones.