IB Mathematics SL Prep

Category - IB Mathematics

A business has decided to resurface a floor section in their warehouse. The section is a square that measures 15 feet on one side. How much is the area that needs to be resurfaced?
  1. 30 square feet
  2. 60 square feet
  3. 215 square feet
  4. 225 square feet
  5. 250 square feet
Explanation
Answer: D - 15 x 15 is 225 square feet.

Key Takeaway: To square any number that ends in 5, use this trick.

Take the first digit of the number, in this case 1. Multiply that by itself and the next consecutive digit, which is 2.

So far, we have 1 x (1+1) = 1 x 2 = 2. Then, simply put 25 on the end, which results in 225. This trick works for squaring any number that ends in 5.
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