Question 1122630
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Since this is multiple choice, it apparently is not a real world question but rather a problem for a math assignment.  In that case, you can do the work to find the answer.<br>
There are 5 surfaces to cover:  2 sides; shallow and deep ends; and the bottom of the pool.<br>
(1) Each side is a trapezoid with bases 2 and 6 and height 25; the area of a trapezoid is the height times the average of the bases.
(2) The shallow end is a rectangle 25x2; the deep end is a rectangle 25x6; I assume you know the formula for the area of a rectangle.
(3) The bottom of the pool is a bit longer than 50m because of the slant.  However, since we are estimating to the nearest thousand and adding 10% for wastage, we can consider it to be a 50x25 rectangle.<br>
The square tiles are 50mm on a side, which is (1/20) meter; so it takes 20*20=400 tiles to cover a square meter.<br>
Figure the total surface area to be covered, multiply by 400 to get the number of tiles, and then add the extra 10%.<br>
One of the answer choices is correct.  You will note that 2 of the 4 answer choices are not even the right order of magnitude.