The shop sold 256 apples on Monday and 137 on Tuesday. Look at this sum on the board: 256 + 137. When we add big numbers like these, which part do you think we should add first, the hundreds or the units? Have a think, then hands up.

The interactive works four column additions, one at a time, from the right. Watch what happens to a column when it reaches ten or more. Read the units along with the screen.

The interactive works four more sums in turn, each one shown with its carries. A pupil comes up and reads each one aloud for the class. As each sum appears, trace with your finger which columns carried and where each carried digit landed, one place to the left.

Here is a fresh bank of four sums, each a little harder: 163 + 214, then 328 + 145, then 456 + 275, then 408 + 195. Say aloud how many columns will carry before we check each answer. The last one hides a zero in the tens column, so add carefully across it.