 Hello and welcome to the session. In this session we discussed the following question which says, if the area of an equilateral triangle is 81 root 3 centimeter square, find its perimeter. Before we move on to the solution, let's recall the formula to calculate the area of an equilateral triangle of side a and this is equal to root 3 a square upon 4 square units. This is the key idea to be used in this question. We know that by Heur's formula, the area of the triangle is given by s into s minus a into s minus b into s minus c where a, b and c are the size of the triangle and this s is equal to a plus b plus c upon 2, that is c, semi perimeter. Now, in equilateral triangle, all the sides are equal, that is, a is equal to b is equal to c. So in this case, s is equal to 3 a upon 2, that is a plus a plus a upon 2, that is 3 a upon 2 and so we get the area of the equilateral triangle equal to root 3 a square upon 4 square units, that is, we got this by substituting s equal to 3 a by 2 in this formula and replacing a, b, c by a. Now, we move on to the solution. We are given that the area of an equilateral triangle is equal to 81 root 3 centimeter square. Now, this gives us root 3 a square upon 4 is equal to 81 root 3, that is, using this formula for the area of equilateral triangle of side a. We get this and from here we get a square is equal to 4 into 81, that is, a square is equal to 2 into 2 into 9 into 9. Now, this gives us a is equal to 2 into 9 equal to 18, that is, the side of the equilateral triangle is equal to 18 centimeters. So, we get the perimeter of the equilateral triangle is equal to 3 a, that is, equal to 3 into 18 equal to 54 centimeters. So, this is our final answer, that is, 54 centimeters is the perimeter of the equilateral triangle. This completes the session. Hope you have understood the solution for this question.