0:00 [Music] welcome to math with mr j [Music] in this video i'm going to cover how to multiply a decimal by a decimal so let's jump right into number one where we have 72 hundredths times 4 tenths now the three steps that we're going to take in order to solve these correctly are at the top of your screen and step one we remove or forget about any decimals and we rewrite the problem so we can rewrite it as 72 times 4 now these decimals will come back into play later in the problem step 2 we multiply just like we would any other whole numbers so 72 times 4 here 4 times 2 is 8. and then 4 times 7 is 28
0:48 and we get 288 there that brings us to step 3 where we need to place the decimal correctly in our answer so we go back up to our original problem and see how many digits are to the right or are behind a decimal however you want to think of it so we have this 7 here this is 1 2 and three i like circling them that way i don't forget anything so that seven the two and the four are all to the right of a decimal that means our answer needs to have three digits to the right or behind the decimal so we can do one of two things with a whole number the decimal comes at the end here and we can think of it like this moving it in
1:34 1 to 3 and placing the decimal here and we get an answer of 288 thousandths which is correct or we can take a look at i'm going to rewrite 288 here we have 1 two three digits behind the decimal and we can just place the decimal there so a couple different ways of thinking of placing that decimal correctly they both will give you the same answer so our final answer is 288 thousandths on to number two where we have six and three tenths times two and nine tenths so first step remove and forget about any decimals
2:20 and we end up with sixty-three times twenty-nine now we multiply nine times three is twenty-seven nine times six is fifty-four plus two is fifty-six done with the 9 done with the 2 we're going a place to the left here so we need our 0 as we work our way over to the 2 2 times 3 is six two times six is twelve so now we add our partial products together seven plus zero is seven six plus six is twelve one plus five is six plus two is eight
3:06 and we have our one over here so we get one thousand eight hundred twenty seven so we need to place our decimal correctly now take a look at the original problem and we have one two digits behind or to the right of a decimal that means our answer needs to have the same thing two digits behind the decimal so we have one two and we can place our decimal here so our final answer is 18 and 27 hundredths so there you have it there's how you multiply a decimal by a decimal i hope that helped thanks so much for watching until next time
3:54 peace
