3rd Grade Math Worksheets Hub Page - Math Salamanders Using these 3rd grade math worksheets will help your child to: learn to add numbers mentally to 100; add on 1, 10, 100 and 1000 to different numbers; learn to add 4 digit numbers in columns; Third Grade Addition Facts Worksheets to 100+100. 4-Digit Addition Worksheets. Free Addition Worksheets (randomly generated)