 Hi, and welcome to the session. Let us discuss the following question. The question says, find the area of a triangle, two sides of which are 18 centimeters and 10 centimeters, and the perimeter is 42 centimeters. Before solving this question, we should first be reversed with Heron's formula. We use this formula for finding the area of a triangle when all its sides are given. This formula states that area of a triangle is equal to square root of s into s minus a into s minus b into s minus c, where a, b and c are the sides of the triangle is the semi-perimeter of the triangle, and this s is equal to 8 plus b plus c by 2. The knowledge of this formula is a key idea in this question. Now begin with the solution. In this question, we have to find the area of a triangle, two sides of which are 18 centimeters and 10 centimeters, and the perimeter is 42 centimeters. Let a, b and c be the sides of the triangle such that c equal to 18 centimeters, b is equal to 10 centimeters, and perimeter of the triangle that is a plus b plus c is equal to 42 centimeters. Now let's first find the value of c. a is equal to 18 centimeters, b is equal to 10 centimeters plus c is equal to 42 centimeters. Now this implies c is equal to 42 centimeters minus 28 centimeters and this is equal to 14 centimeters. Let's now calculate the semi-perimeter of the triangle. We know that s is equal to a plus b plus c by 2. Now substitute the values of a, b and c. a is equal to 18 centimeters, b is equal to 10 centimeters, c is equal to 14 centimeters upon 2, and this is equal to 42 centimeters by 2, and this is equal to 21 centimeters. So semi-perimeter of the triangle is 21 centimeters. Now let's calculate s minus a, s is equal to 21 centimeters, a is equal to 18 centimeters, so this is equal to 3 centimeters, s minus b is equal to 21 centimeters minus 10 centimeters, this is equal to 11 centimeters, s minus c is equal to 21 minus 14 centimeters, and this is equal to 7 centimeters. By Heuron's formula, we know that area of a triangle is equal to square root of s minus a into s minus b into s minus c. Now substitute the values of s, s minus a, s minus b and s minus c in this. s is equal to 21 centimeters, s minus a is equal to 3 centimeters, s minus b is equal to 11 centimeters, s minus c is equal to 7 centimeters. Now this is equal to square root of, now 21 can be written as 3 into 7 into 3 into 11 into 7 centimeters square, and this is equal to 21 into square root of 11 centimeters square. Always remember to write the unit. Hence the required area of the triangle is 21 into square root of 11 centimeters square, this is our required answer, so this completes the session, I can take care.