Question 94
MediumOriginal questionA school numbers its 60 students from 1 to 60 and puts each in a house by the remainder of the roll number on division by 5: remainder 1 is Red, 2 Blue, 3 Green, 4 Yellow and 0 White.
Which pair of roll numbers are in the same house?
Show the answer and explanation
CorrectNot quiteAnswer A
Correct answer: A
Explanation
Two numbers share a house when they are congruent modulo 5, that is, their difference is a multiple of 5.
: both are Green. The other differences are 27, 27 and 19.
Worth noting
14 and 41 use the same digits, but is not a multiple of 5.
- Concept
- Congruent numbers share a class
- Typical timeTypical
- 120 s
- Your timeYours
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Ten questions from Modulo Arithmetic & Congruence, at your own pace.