alleryStart learning →A number 10x + y is divisible by 7 exactly when which expression is?
Ax + 2y
B2x - y
Cx - 2y
Dx + y
Answer & Solution
Correct answer: C. x - 2y
Subtracting twice the last digit from the rest preserves divisibility by 7, because 10x + y is 10 times (x - 2y) plus 21y.
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