Adding and subtracting whole hundreds is mental math that comes from knowing what a hundred is. 300 + 400 is three hundreds and four hundreds, which is seven hundreds, or 700. 846 - 600 takes six hundreds away from eight hundreds and leaves two, with the 46 untouched, so the answer is 246. Second graders are expected to do this without regrouping or drawing blocks.
This worksheet gives twenty equations on one page, adding two whole hundreds or taking whole hundreds from a three-digit number, and a line for each answer. Ask your child to say the hundreds out loud, for example eight hundreds take away six hundreds, and then to read the whole number back aloud to check it.
What your child will learn
Add whole hundreds in your head
Subtract whole hundreds from a three-digit number
Keep the tens and ones when subtracting hundreds
Common Core standard: 2.NBT.B.8
Worked example
300 + 400 is 3 hundreds and 4 hundreds, which is 7 hundreds: 700. 846 - 600 leaves 2 hundreds and keeps the 46: 246.
Common mistake
Changing the tens or ones digit when only the hundreds should change.
Helpful hint
Think in hundreds: 8 hundreds minus 6 hundreds is 2 hundreds.