A four digit code has to be entered into this keypad to open the door to a safe. There are four rules: • The code must be an even number • There must be at least one digit from each row • There must be at least one digit from each column • When you add the digits together it makes an even number Which code is correct?
A 1368 B 1458 C 1569 D 2378 E 2678
A
The four rules, each based on a mathematical idea (even, row, column), eliminate in turn one of the options. The first rule eliminates option C, the second rule option D, the third rule option B, the fourth rule option E; leaving option A as the code fitting all the rules.
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