Intro Quiz: Multiplication of two decimals

Video: Multiplication of two decimals

﻿Hi, I'm Miss Davies, and in this lesson we're going to be multiplying together two decimals. When multiplying two decimals together, the easiest way to do it is to multiply by a power of 10 to make the numbers in the question into integers. To make 5.3 an integer, we're going to multiply it by 10. This gives us 53. We're going to do the same to 3.4 to get 34. We only need to multiply it by 10, as there is only one number after the decimal point. We can now work out 53 multiplied by 34. It is up to you which method you use for multiplication. Do whatever feels right and whatever you are used to. Whichever methods you use, you should get an answer of 1,802. So 53 multiplied by 34 is equal to 1,802. We need to work out the answer to 5.3 multiplied by 3.4. To go from 53 to 5.3, we divide by 10. To go from 34 to 3.4, we also divide by 10. This means that we need to divide 1,802 by 100. This gives us an answer of 18.02. We have been asked to work out 2.45 multiplied by 4.1. First, we need to multiply these to get integers. As there are two decimal places in 2.45, we need to multiply this by 100. This gives 245. 4.1 has only one decimal point, so let's multiply this by 10 to get 41. The answer to this calculation is 10,045. To go from 245 to 2.45, we divide by 100. To go from 41 to 4.1, we divide by 10. This means we need to divide 10,045 by 1,000. This gives us an answer of 10.045. Next we are working out 0.7 multiplied by 23.1. As both of these numbers only have tenths, we're going to multiply both of them by 10. This gives us seven multiplied by 231, which is 1,617. As we have multiplied both of the numbers by 10, we need to divide them by 10 now. This means we need to divide our whole final answer by 100 overall. This gives an answer of 16.17. Here are some questions for you to try. Pause the video to complete your task and resume once you're finished. Here are the answers. If there's an integer in the question, you don't need to multiply this by a power of 10. Make sure that when you've done your multiplication, you're dividing this answer by whatever you multiplied the two initial numbers by to get your final answer. Here is a question for you to try. Pause the video to complete your task and resume once you're finished. Here is the answer. Steve needs a total of eight metres of pipe. Eight multiplied by one pound 24 gives an answer of nine pound 92. Here is a question for you to try. Pause the video to complete your task and resume once you're finished. Here is the answer. Mo has put the decimal point in the wrong position. The correct answer is 15.54. That's all for this lesson. Thanks for watching.

Maths

Multiplication of two decimals

Introductory Quiz

Video

Worksheet

Final Quiz

Lesson Complete