Missing Operators


Who Wants to Be a Euronaire? What is the missing symbol from this mathematical sentence that would make it true?


(5


Is it: A. (5 + 3) + 7


B. (5 – 3) + 7 3) + 7 = 22 C. (5 × 3) + 7 D. (5 ÷ 3) + 7


You may not be able to phone a friend, but if you’re not sure, you could ask the audience!


1. Put the correct symbols into these. a) 8 + (9 d) 12


6) = 23 g) 24 – (17


(33 ÷ 11) = 4 9) = 16


b) (4 × 2) e) (7


3 = 24 h) (42 ÷ 6) (5


5) – 10 = 25 9 = 63


But what if both operators are missing, like in this one? 14


2) = 2


There are lots more possibilities now. We can narrow down the possibilities by using common sense.  Both symbols will not be × because the answer is too small.  Both symbols will not be + because the answer is too small.  If we look at the first number and the answer, we get a very good idea.


What must you do to 14 to get an answer of 2? 14 ÷ 7 = 2


We know that the operation inside the brackets must give us an answer of 7. You should now know what symbol to use.


2. Try these. a) 7 d) 6


g) 45


(4 (2


(5


(24 (8


5) = 63 5) = 60 4) = 5


35) = 78 e) 143 3) = 35


b) 9 e) 7 h) 6


(3 (9


(14


6) = 18 3) = 21


5) = 54


3. Now use your calculator to work out the missing symbols. a) 19 c) 14


3) = 70 (36 130 Rules and Properties


b) 83 d) 56 f) 24


c) 32 f) 21 i) 11


(76 (24 (76


(4


(15 (84


38) = 121 6) =14


19) = 34656 2) = 4 6) = 12 7) = 132


c) (9 – 5) f) 36 ÷ (8 i) 8 × (10


7 = 11 4) = 3


2) = 64


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