Khan/khan-exercises — Issue #5149: Divisibility - Possible Divisibility Problem Correction?
Author: KhanBugz
Created: 2011-10-28 21:14:32+00:00
State: open
Labels: chrome, win7

Problem:
All numbers divisible by 10 and 18 are also divisible by which of the following?

Multiple choice:
69, 47, 30, 85, 36

Issue:
From my perspective, it seems there are two correct answers available here, 30 and 36. Choosing 36 is marked as incorrect, while 30 is marked as correct by the system.

Rationale:
Factorization of 10 is 2 * 5.
Factorization of 18 is 2 * 3 * 3.

Our pool of available factors is 2 * 2 * 3 * 3 * 5.

From this we can create:
36: 2 * 2 * 3 * 3
30: 2 * 3 * 5

[divisibility.html?seed=11&problem=0](http://sandcastle.khanacademy.org/media/castles/Khan:master/exercises/divisibility.html?seed=11&problem=0&debug)

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