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curriculum/challenges/english/10-coding-interview-prep/project-euler/problem-90-cube-digit-pairs.md

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+---
+id: 5900f3c61000cf542c50fed9
+challengeType: 5
+title: 'Problem 90: Cube digit pairs'
+forumTopicId: 302207
+---
+
+## Description
+<section id='description'>
+
+Each of the six faces on a cube has a different digit (0 to 9) written on it; the same is done to a second cube. By placing the two cubes side-by-side in different positions we can form a variety of 2-digit numbers.
+
+For example, the square number 64 could be formed:
+
+<img class="img-responsive center-block" alt="two cubes, one with the number 6 and the other with number 4" src="https://cdn-media-1.freecodecamp.org/project-euler/cube-digit-pairs.png" style="background-color: white; padding: 10px;">
+
+In fact, by carefully choosing the digits on both cubes it is possible to display all of the square numbers below one-hundred: 01, 04, 09, 16, 25, 36, 49, 64, and 81.
+
+For example, one way this can be achieved is by placing {0, 5, 6, 7, 8, 9} on one cube and {1, 2, 3, 4, 8, 9} on the other cube.
+
+However, for this problem we shall allow the 6 or 9 to be turned upside-down so that an arrangement like {0, 5, 6, 7, 8, 9} and {1, 2, 3, 4, 6, 7} allows for all nine square numbers to be displayed; otherwise it would be impossible to obtain 09.
+
+In determining a distinct arrangement we are interested in the digits on each cube, not the order.
+
+<div style="margin-left: 4em;">
+  {1, 2, 3, 4, 5, 6} is equivalent to {3, 6, 4, 1, 2, 5}<br>
+  {1, 2, 3, 4, 5, 6} is distinct from {1, 2, 3, 4, 5, 9}
+</div>
+
+But because we are allowing 6 and 9 to be reversed, the two distinct sets in the last example both represent the extended set {1, 2, 3, 4, 5, 6, 9} for the purpose of forming 2-digit numbers.
+
+How many distinct arrangements of the two cubes allow for all of the square numbers to be displayed?
+
+</section>
+
+## Instructions
+<section id='instructions'>
+
+</section>
+
+## Tests
+<section id='tests'>
+
+```yml
+tests:
+  - text: <code>cubeDigitPairs()</code> should return a number.
+    testString: assert(typeof cubeDigitPairs() === 'number');
+  - text: <code>cubeDigitPairs()</code> should return 1217.
+    testString: assert.strictEqual(cubeDigitPairs(), 1217);
+
+```
+
+</section>
+
+## Challenge Seed
+<section id='challengeSeed'>
+
+<div id='js-seed'>
+
+```js
+function cubeDigitPairs() {
+
+  return true;
+}
+
+cubeDigitPairs();
+```
+
+</div>
+
+
+
+</section>
+
+## Solution
+<section id='solution'>
+
+```js
+// solution required
+```
+
+</section>