 Hi and welcome to the session. Let us just ask the following question. The question says there is a slide in a power. One of its sidewall has been painted in some color with a message keep the power green and clean. See figure 12.10. This is the figure 12.10. If the sides of the wall are 15 meters, 11 meters and 6 meters find an area painted in color. Look at this figure. This is the sidewall which has been painted with some color with a message keep the power green and clean. Sides of this sidewall are 11 meters, 15 meters and 6 meters. We have to find the area of painted portion. Clearly area of the painted portion is equal to area of the sidewall. So keeping all this in mind let us now begin with the solution. Let us first find the area of the sidewall measuring 5 meters, 11 meters and 6 meters. Let A is equal to 15 meters, B is equal to 11 meters and C is equal to 6 meters. We will use Heron's formula for finding the area of sidewall. Let us first calculate semi perimeter. 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 15 meters, B is equal to 11 meters and C is equal to 6 meters and this is equal to 32 meters by 2 and this is equal to 16 meters. Let us now calculate S minus A equal to 16 meters and A is equal to 15 meters so S minus A is equal to 1 meter. S minus B is equal to 16 meters minus 11 meters and this is equal to 5 meters. S minus C is equal to 16 meters minus 6 meters and this is equal to 10 meters. Now area of the sidewall is equal to square root of S into 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 16 meters, S minus A is equal to 1 meter, S minus B is equal to 5 meters, S minus C is equal to 10 meters. Now this is equal to square root of 800 meters square and this is equal to 800 is equal to 4 into 4 into 5 into 5 into 2 meters square and this is equal to 20 into root 2 meters square. We know that area painted in color is equal to area of the sidewall. Area of sidewall is 20 into root 2 meters square so area painted in color is 20 into root 2 meters square. This is our required answer so this completes the session. Bye and take care.