Video Transcript
Find 42 plus 29. Hint: Do you have to regroup ones
to make a 10?
In this question, we have to find
the sum of two two-digit numbers, the number 42 and 29. And we can see that the
calculation’s been set out using the column method. We can see that 42 has four 10s and
two ones. And we’re adding 29, which has two
10s and nine ones. We always start by adding in the
ones column. We need to add two and nine. Two and nine is 11. But we can only write one digit in
our ones column. We know that 11 is 10 and one
more. So we write the ones digit in the
ones column and one 10 in the tens column. 11 is one 10 and one one. We’ve exchanged 10 ones for one
10. And we’ve written this 10 above our
other 10s to help remind us to add it to our other 10s when we’re adding in the tens
column.
Now we can add the tens. We have four 10s in the number 42
and two 10s in the number 29. Four 10s plus two 10s gives us a
total of six 10s. But let’s not forget we have
another 10 which we’ve exchanged. Six 10s plus one 10 gives us a
total of seven 10s. We added 42 and 29 to give us our
answer of 71. First, we added the ones, and we
had a total of 11. So we had to regroup 10 of our ones
to make a 10. Then we added our 10s. We had six 10s and we added the one
we’d regrouped, which gave us a total of seven 10s. 42 plus 29 equals 71.
