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Grade 4 Math · Level 1, Numbers Through One Million

Multi-Digit Addition & Subtraction

How the lesson starts: Multi-Digit Addition & Subtraction

1. The bolt factory

   Beep boop, hello! Welcome to the robot factory. Robots Bolt and Gizmo count giant piles of bolts. Today they have 45,678 bolts, and 28,457 more arrive. Let's help them add and subtract!

2. Column adding

   Bolt stacks 45,678 on top of 28,457, ones under ones. Ones: 8 + 7 = 15, write 5, carry 1. Tens: 13, carry 1. Hundreds: 11, carry 1. Thousands: 14, carry 1. Ten-thousands: 7. Total: 74,135!

3. Borrow across zeros

   Now subtract: 60,000 − 23,457. The ones place has 0, so borrow! Borrow from the 6 all the way down. The 6 becomes 5. Each zero becomes a 9. The ones get 10. Now subtract each place: 36,543!