Good morning this week we carry on with addition and subtraction. So today's lesson is really a review of last week.
Starter: In pairs, create a 2-digit number by rolling a 0-9 dice or using numbered cards 0-9, and write how many more are need to make the next multiple of 10. Repeat.
Using the questions below you are going to add or subtract a single digit from a two digit number. You will need to use your number bond knowledge for this. Questions 1 - 8 are not going to be too challenging as these are just completing a number bond. e.g. 45 + 5 = You will know that 5 + 5 is 10. Therefore 40 + 10 = 50.
Questions 9- 16 however, will cross a ten. This is where we can use our knowledge of how a number is made up. The different combinations that can be used. For instance 5 can be made of 2 and 3 or 1 and 4 or 3 and 2.
So if I have a calculation that says 42 - 5 = I could take away two first to get an answer of 40, then take away three to get an answer of 37. Some of you will do this automatically in your head, others may need to see the process. See picture below.
Some will choose to count back along a number line or ruler. Again see the picture below. Either way is fine, we choose the method that works best for us.
Now have a go at our Mastery Challenge. The champions challenge does say to do it mentally (in our fabulous brains), but don't forget to show workings out as you can always challenge yourself with the inverse operation to check your answer is correct. e.g. if Mrs R-J has 42 chocolate fudge cakes and Mrs Edwards came and ate five of them. How many deliciously scrumptious chocolate fudge cakes has Mrs R-J got left?
What I need to do to answer the question: 42 - 5 = 37
Using the inverse to check my answer: 37 + 5 = 42