Video Transcript
Take away eight from 42. Hint: Regroup one 10 into 10
ones.
In this question, we have to
subtract our one-digit number, eight, from a two-digit number, 42. And we have to use the column
subtraction method. The calculation has been written
out for us. So we can start subtracting. When we’re subtracting using the
column subtraction method, we always start subtracting in the ones column. 42 has four 10s worth 40 and two
ones. We can model this number using four
tens blocks and two ones blocks. So we have two ones and we need to
subtract eight ones. You may have already realized we
don’t have enough ones to subtract eight. Two is less than eight.
Luckily, the question has given us
a hint. We’re told we need to regroup one
10 into 10 ones. This means we need to take one of
our 10s and we group it into 10 ones. So now we have three 10s and 12
ones. We need to make a note of what
we’ve done to our number. We can cross out our two ones and
write 12 ones. And we don’t have four 10s
anymore. We have three. Now that we’ve regrouped, we can
subtract in the ones column. 12 ones take away eight ones leaves
us with four ones. Now we just need to subtract in the
tens column. Because we’re subtracting a
one-digit number from a two-digit number, there’s nothing to subtract from our
tens. Three 10s take away no 10s leaves
us with three 10s. We took away eight from 42 using
the column subtraction method. 42 subtract eight equals 34.
