Monday, January 3, 2011

Perimeter PSLE 2010 P1 Q13

A floor is covered with a row of equilateral triangular tiles of side 3 cm. The perimeter of the floor covered by the tiles is 93 cm. How many tiles are used to cover the floor?  Ans: 29 (Option 2)

93 / 3 = 31 sides

31 - 2 =  29   Remove the 2 sides to avoid double counting

Alternative method

93  -  3  -  3  =  87      Remove the lengths of both sides

87/3  =  29       Divide by the length of each side


  1. it's correct!! i put 29 also :D

  2. correct. because side of 1 triangle is 3cm, and total perimeter of figure is 93cm. the no. of sides on the bottom of the figure is 1 more than the no. of sides on the top of the figure. Hence, use 93cm/3cm =31cm, which is the total no. of sides in the figure. Subtract the 2 sides at the left & right to give you 29 sides. Since the no. of sides on top is 1 less than the no. of sides at the bottom, there will be 14 sides on top and 15 sides below. The no. of tiles will be (no. of sides at the bottom)+(no. of sides at the bottom-1)=29