Free Printable Math Worksheets for Grade 4 - Homeschool Math All worksheets come with an answer key placed on the 2nd page of the file. Mental addition Complete the next whole hundred (missing addend) Adding 2-digit numbers mentally Adding 1-and 2-digit numbers mentally (3 addends) Adding whole tens (4 addends) (print in landscape) Adding whole hundreds (2 addends) (print in landscape)