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Nines and threes I am learning to decide if a number is divisible by nine or three. Can the number be shared evenly between 9 or 3. To work out whether a number is divisible by nine add the digits together. If the number you make is on your nine times table then your original number is divisible by nine. e.g. 72 7 + 2 = 9, 9 is on my 9 times table so 72 is divisible by 9. Let’s find out why this works. 72 is shown below. If we remove 1 from all the groups of ten then they will all have 9. 9 can easily be shared between 9 (9 ÷ 9 = 1) You can see from this that 72 is divisible by 9. Now there are 9 ones left. (9 ÷ 9 = 1) 72 10 9 10 9 10 9 10 9 10 9 10 9 10 9 7 + 2 =9 Can 119 be divided by 9? 119 is shown below. If we remove 1 from the 100 we will have 99. This amount can be evenly shared between 9 (99 ÷ 9 = 11) If we remove 1 from the group of ten we will have 9 in the group. This amount can be shared between 9 (9 ÷ 9 = 1) . Now there are 11 ones left. 11 can’t be evenly shared among 9 groups so 119 is not divisible by 9. 119 1 100 99 10 9 + 1 + 9 = 11 So 119 is not divisible by 9 Use this strategy to work out whether the numbers below are divisible by 9. The first one has been done for you. 1) 333 Yes, (3 + 3 + 3 = 9) 2) 252 Yes, (2 + 5 + 2 = 9) 3) 114 No, (1 + 1 + 4 = 6) 4) 432 Yes, (4 + 3 + 2 = 9) Click again when you have worked out all your answers. 5) 227 No, (2 + 2 + 7 = 11) Need some more practise? Try Pg47 & 48 of Teacher Tools Multiplication and Division Book Numeracy resources