Objective:
To practice these math problems of 1.NBT.C.5 worksheets, students are required to mentally find 10 more or 10 less than a given two-digit number without having to count by ones and explain the reasoning used. Users can directly refer the answer key to verify the work with steps for the corresponding practice problems given in the 1.NBT.C.5 activities under common core state standards for 1st grade mathematics.