To raise money for charity, 28865 boys and 49788 girls took part in sports activities. How many children took part in total?
We’re told that a group of children are raising money for charity. And the key information here is the number of boys which is 28865 and also the number of girls which is 49788. We’re asked to calculate the number of children that took part in total. And the word total gives us a clue that we’re going to have to add to find the answer. We need to add together these two five-digit numbers that we’ve been given. This addition looks a little complicated to work out mentally. So what other strategy could we use?
We could use vertical addition. First, we need to write the numbers on top of each other, making sure that we write each digit in the correct column. And it doesn’t matter which way around we write these numbers. So let’s start with the larger number first: 49788 plus 28865 and all our digits are lined up. First, let’s add the ones. Eight ones plus five ones equal 13 ones. And we can write a three in the ones place and then exchange 10 of our ones for one ten.
Onto the tens, eight tens plus six tens equal 14 tens. But we’ve already exchanged one 10 as well. So that’s 15 tens. So we’ll write the five in the tens place and then exchange 10 of our tens for 100. Seven hundreds plus eight hundreds equals 15 hundreds. We’ve already exchanged 100. So that makes 16 hundreds. So we’ll write the six in the hundreds column and then exchange 10 hundreds for 1000. Lots of exchange is going on in this calculation. 9000 plus 8000 equals 17000 and we’ve also got 1000 underneath. That’s 18000. So we’ll write an eight in the thousands column and then exchange 10000s for one lot of 10000. And finally, four lots of 10000 plus two lots of 10000 equals six lots of 10000. We’ve also got one underneath. So that seven lots of 10000 or 70000.
And so, if the number of boys that take part in sports activities is 28865 and the number of girls is 49788, the number of children that took part in total is 78653. We found the answer using column addition.