How to Subtract Decimals | Math with Mr. J

[Music] welcome to math with mr j [Music] in this video i'm going to cover how to subtract decimals now if you're able to subtract whole numbers you're going to be able to subtract decimals there's just a couple of different steps as far as how we set these problems up let's jump into our examples and start with number one where we have 29 and eight tenths minus five and seventy three hundredths so the first thing that we want to do line our decimals up meaning we'll have 29 and 8 tenths minus 5 and 73 hundredths so the decimals are lined up that's going to line up all of our places so the hundredths tenths ones tens whatever places you're working with within the problem the problem does look a little offset the five and seventy three hundredths goes further to the right than the 29 and eight tenths that's okay the most important part we have our decimals lined up now we can use placeholder zeros to make this problem look a little more lined up meaning we can place a zero in the hundredths place right here we're using placeholder zeros to better align the problem remember zeros to the right of a decimal do not change the value that's an equivalent decimal there so we're not changing the value of that number or the problem overall now we're ready to subtract so we start with zero minus three so we're going to need to borrow so let's borrow from this eight and now we have ten minus three which is seven then we move to the tenths where we have seven minus seven which is zero now bring our decimal straight down the decimal should be lined up throughout the entire problem even in the answer so we place the decimal in our answer by bringing it straight down then we move to the ones where we have nine minus five which is four and then lastly the tens place we have two minus zero we don't have anything in the tens place for five and seventy three hundredths so let's just bring that two down and our final answer is twenty-four and seven hundredths now before moving to number two i do want to mention a couple of common mistakes when we subtract decimals the first one being let me rewrite the problem here 29 and 8 10 minus five and seventy-three hundredths so the first mistake would be dropping this three here assuming that we can just drop the three but in reality remember we have a zero here and we need to borrow so don't just drop a number if there is nothing above it we need to use borrowing because there is a 0 there the other mistake would be lining the problem up like this so lining up the digits instead of lining up the decimals so in the case of this right here you can see that the decimals aren't lined up we have three digits above three digits remember line the decimals up so this will not give a correct answer let's move on to number two and try another example so we have 168 and nine hundredths minus 31 and 452 thousandths let's use a placeholder zero so everything goes over to the thousandths place and now we're ready to subtract don't drop that two because we have zero minus two there and we need to borrow so let's borrow from the nine and now we have ten minus two which is eight so an eight in the thousandths then we move to the hundredths so eight minus five which is three now for the tenths so we have zero minus four we're going to need to borrow ten minus four is six remember bring your decimal straight down it should be lined up throughout the entire problem when we subtract decimals then we move to the ones so seven minus one is six then the tens so six minus three is three and then finally the hundreds where we have a one minus zero there so we can just drop the one and we have an answer of 136 and 638 thousandths so there you have it there's how you subtract decimals i hope that helped thanks so much for watching until next time peace