Subtracting and renaming through zero

In Primary 2, you subtracted in columns and renamed one ten as ten ones. One thousand can also be renamed as ten hundreds. Today, we subtract numbers up to ten thousand and rename across zeros. A science centre printed five thousand and six tickets. It used two thousand, three hundred and forty-eight tickets. How many tickets were left? We must find how many tickets were left. So we subtract the tickets used from the tickets printed. Write the tickets printed on top, and the tickets used below, ones under ones. Start with the ones. We cannot subtract eight ones from six ones. The tens and the hundreds are zero, so rename one thousand as ten hundreds. Five thousands become four thousands. Now the hundreds have ten hundreds. Rename one hundred as ten tens. Ten hundreds become nine hundreds. Now the tens have ten tens. Rename one ten as ten ones. Ten tens become nine tens. Ten ones and six ones make sixteen ones. Now the ones. Sixteen minus eight is eight. Now the tens. Nine minus four is five. Now the hundreds. Nine minus three is six. Now the thousands. Four minus two is two. Two thousand, six hundred and fifty-eight tickets were left.

A science centre printed seven thousand and forty-two tickets. It used one thousand, six hundred and twenty-five tickets. How many tickets were left? Try it first. Pause if you like. We cannot subtract five ones from two ones, so rename one ten as ten ones. Four tens become three tens. Ten ones and two ones make twelve ones. Now the ones. Twelve minus five is seven. Now the tens. Three minus two is one. We cannot subtract six hundreds from zero hundreds, so rename one thousand as ten hundreds. Seven thousands become six thousands. Now the hundreds have ten hundreds. Now the hundreds. Ten minus six is four. Now the thousands. Six minus one is five. Five thousand, four hundred and seventeen tickets were left.

A science centre printed eight thousand and three tickets. It used four thousand, five hundred and sixty-seven tickets. How many tickets were left? Try it first. Pause if you like. We cannot subtract seven ones from three ones, and the tens and the hundreds are zero. So rename one thousand as ten hundreds, and eight thousands become seven thousands. Now the hundreds have ten hundreds. Rename one hundred as ten tens. Ten hundreds become nine hundreds. Now the tens have ten tens. Rename one ten as ten ones. Ten tens become nine tens. Ten ones and three ones make thirteen ones. Now the ones. Thirteen minus seven is six. Now the tens. Nine minus six is three. Now the hundreds. Nine minus five is four. Now the thousands. Seven minus four is three. Three thousand, four hundred and thirty-six tickets were left. Start with the ones, and when a place does not have enough, rename one from the place on its left, even across zeros.