Description: Learn to multiply a 4-digit number by a 1-digit number. In this video, we will multiply 8085 times 9. Created by Sal Khan. We can write the 5 in the ones place and carry the 5 to the tens place. And we're going to calculate 9 times 8 and then add the 4 that we just carried. So we'll write the 6 right here the tens place and carry the 7.*Teacher Advisor is 100% free.