4th grade math practice with decimals continued

Learning how to multiply and divide decimals is a bit different from adding and subtracting decimals, but it is easy once you practice!  When adding and subtracting decimals, we brought the decimal point straight down where our answer would be after adding place holders to help us.  When multiplying decimals, you would first multiply your numbers together like you normally would.  When finished, you then have to count how many numbers there are after each decimal point.  Then, you count from the right of your answer to the left however many digits you counted after your decimals, and place your decimal point in your answer.  For example, to multiply 16.58 x 37.2, we would first multiply the numbers together and forget about the decimal points.  So 1658 x 372 = 616776.  Now you look at your original problem and count the number of digits after your decimal points: 16.58 x 37.2.  There are three digits after the decimals.  So we take our answer we got, 616776 and count from the right to the left 3 digits.  So, now our final answer is 616.776.  For a video on how to multiply decimals, go to http://www.youtube.com/watch?v=EDd9xaGNP_Q.  To divide decimals, you first need to use your long division skills! (yes, I know you may hate long division, but we will get through this =)).  We will review an example of a long division problem to begin.  Use long division to divide 54.0 / 2.5.  Which number goes on the outside and inside of the division bar?  The number on the bottom of the fraction, or in our case to the right after the slash, goes on the outside of the division bar.  And our numerator, or number to the left of the slash, always goes on the inside.  So, looking our decimal points, we must move those decimal points to the right.  For our number outside the division bar: 2.5, we would only have to move our decimal over once to the right to make a whole number.  Since we moved the decimal over once in 2.5, we are going to move our decimal over once in 54.0.  Important to note: however many times you move your number's decimal outside the division bar, you must move your number's decimal inside the division bar to the right the same amount of times.  In our case, we would move the decimal in 2.5 over once to the right to make 25. .  Now, in the same manner, move the decimal in 54.0 to the right once to make 540. .  Now we may begin to divide since we got rid of our decimals.  We must find how many times 25 goes into 54, meaning 25 multiplied by what is closest to 54?  25 goes into 54 twice because 25 x 2 = 50, which is closest to 54.  Now write the 2 above the 4, and write 50 underneath 54, then subtract.  Now, bring your zero down and proceed.  Now our question is,  how many times does 25 go into 40?  25 goes into 40 once, so now place your 1 above your zero in 540.  Next, write your 25 underneath your 40 and subtract.  You should get 15.  Now, we must add a place holder to our 540 and bring that down to our 15, making it 150.  Then, we must find how many times 25 goes into 150.  You will find that 25 x 6 = 150 exactly.  Because of this, we are done dividing.  Now we must worry about our decimal in our final answer.  All you have to do is move your decimal up from 540, so our final answer is 21.6.  You can always check your answer by multiplying 21.6 x 2.5.  For more practice, you can visit the video: http://www.youtube.com/watch?v=AZ6fyQDVqEE.  And for more practice with long division, visit: http://www.softschools.com/math/division/long_division/.

These are examples of dividing and multiplying decimals: