Question 1070394
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<pre>
{{{1200/15}}} = 80 tiles along the longest side, and

{{{900/15}}} = 60 tiles along the shortest side.

In all, 80 * 60 = 4800 tiles.

The total cost is 7*4800 = rs 33600.
</pre>

The solution by DENNIS_DON is WRONG.