"A pebble dropped in still water sends its ripple forward, never backward. So it is with carrying."

The Ripple

When the ones digits add up to more than 9, the extra simply ripples forward. Watch.

Example 1: 67 + 28 Break it: 28 = 20 + 8 Add tens: 67 + 20 = 87 Add ones: 87 + 8 = 95 \leftarrow the 1 ripples into the tens

Example 2: 46 + 37 Break it: 37 = 30 + 7 Add tens: 46 + 30 = 76 Add ones: 76 + 7 = 83 \leftarrow the 1 ripples forward again

Your turn. These all involve a carry — just let it ripple.

58 + 36 =

75 + 18 =

49 + 43 =

Insight

When ones overflow past 9, the extra simply ripples into the tens. No need to go back — just keep moving forward.

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