Adding up to four digits

In Primary 2, you added in columns and renamed ten ones as one ten. Here are ten discs of one hundred. Ten hundreds make one thousand. Today, we add numbers up to ten thousand in columns, from the ones to the thousands. On Saturday, two thousand, six hundred and forty-eight people visited a science centre. On Sunday, three thousand, seven hundred and twenty-five people visited it. How many people visited on the two days altogether? We must find the total number of people. So we add the two numbers. Write Saturday's number on top. Write Sunday's number below it. Line up the ones under the ones. The columns are thousands, hundreds, tens and ones. Start with the ones. Eight plus five is thirteen. Rename thirteen ones as one ten and three ones. Write the one ten on top of the tens. Now the tens. Four plus two is six. Add the 1 on top. Six plus one is seven. Now the hundreds. Six plus seven is thirteen. Ten hundreds make one thousand. Rename thirteen hundreds as one thousand and three hundreds. Write the one thousand on top of the thousands. Now the thousands. Two plus three is five. Add the 1 on top. Five plus one is six. Six thousand, three hundred and seventy-three people visited on the two days.

A school library has four thousand, three hundred and fifty-two storybooks and one thousand, eight hundred and thirty-four science books. How many books does it have altogether? Try it first. Pause if you like. Start with the ones. Two plus four is six. Five plus three is eight. Now the hundreds. Three plus eight is eleven. Ten hundreds make one thousand. Rename eleven hundreds as one thousand and one hundred. Write the one thousand on top of the thousands. Now the thousands. Four plus one is five. Add the 1 on top. Five plus one is six. The library has six thousand, one hundred and eighty-six books altogether.

A bakery sold six thousand, four hundred and fifty-eight buns in May and seven hundred and twenty-nine buns in June. How many buns did it sell in the two months? Try it first. Pause if you like. Seven hundred and twenty-nine has no thousands. Its 7 is 7 hundreds, so it goes under the hundreds. Start with the ones. Eight plus nine is seventeen. Rename seventeen ones as one ten and seven ones. Write the one ten on top of the tens. Now the tens. Five plus two is seven. Add the 1 on top. Seven plus one is eight. Now the hundreds. Four plus seven is eleven. Ten hundreds make one thousand. Rename eleven hundreds as one thousand and one hundred. Write the one thousand on top of the thousands. Now the thousands. Six plus the 1 on top is seven. The bakery sold seven thousand, one hundred and eighty-seven buns in the two months. Line up the places, start with the ones, and rename ten of a place as one of the next place.