For the final step we multiply the tens digits.
6 × 8 = 48
We add the 5 that was carried.
48 + 5 = 53
The answer is 5,372.
Test yourself
Try these for yourself:
a) 64 × 69 =
b) 34 × 78 =
Here are the answers:
a) 4,416
b) 2,652
Let’s work through the second problem together.We begin by multiplying 4 times −2, which equals −8. Borrowing 10 we have 2 left. We carry the −10 to the next column as −1
(times 10).
Now we multiply crossways. Eight times 4 is 32, plus 3 times −2 is −6. Adding −6 is the same as subtracting 6 from 32, which gives
us 26. Don’t forget the carry of −1, so we end up with 25. Write the 5 and carry the 2. For the final step we multiply the tens digits:
3 × 8 = 24. We add the 2 which we carried to get 26. We now have our answer, 2,652.This is simply a method you might like to play with. Experiment with problems of your own.