There is something wrong with the figures given in this question: if ∠ A = 30, AB = 55 cm, and AD = 40 cm, then according to the nature of a right triangle (the opposite side of a 30-degree angle is equal to half of the hypotenuse), BD should be 27.5 cm, while according to Pythagorean theorem, the square of AB = the square of AD+the square of BD, but in fact the square of 55 is not equal to.