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Divisible Digits

Age 11 to 14
ShortChallenge Level Yellow star
Secondary curriculum
  • Problem
  • Solutions

Answer: 9540


Using divisibility tests
9  5   ___   ___
9  5   ___  (0 or 5) (since divisible by 5)
9  5   ___   0 (divisible by 6, so even)

Divisible by 3 $\Rightarrow$ sum of digits a multiple of 3
9 + 5 = 14, so this digit can be 1, 4 or 7
9510, 9540 or 9570

Divisible by 4 $\Rightarrow$ last 2 digits divisible by 4
9540

Note: You can apply the divisibility tests in a different order, but some orders will take longer than others!


Finding a larger number that the number must be divisible by
The number is divisible by 3, 4, 5 and 6, so it is divisible by 60 (lowest common multiple).

The number is less than 9600. 96 = 60 + 36, so 96 is a multiple of 6, so 960 is a multiple of 60 and therefore 9600 is a multiple of 60.

Multiples of 60: 9600, 9540, 9480

Only 9540 begins 95.

You can find more short problems, arranged by curriculum topic, in our short problems collection.

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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