alleryIn the subtract-twice test for 7, you subtract twice the last digit from what?
AThe whole original number
BThe number made by the rest
CThe sum of all the digits
DThe first digit of it
Answer & Solution
Correct answer: B. The number made by the rest
1. Write the number as 10x + y, where y is the last digit.
2. Subtract twice the last digit from the number formed by the remaining digits, that is x - 2y.
3. The number is divisible by 7 exactly when that result is.
_Source: Wikipedia, Divisibility rule, section Divisibility by 7_
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