11. (a) एक त्रिभुज की दो भुजाएँ 15 m और 20 m हैं तथा त्रिभुज की परिमिति 60 m है।
त्रिभुज का क्षेत्रफल ज्ञात कीजिए।

300m

After doing google translation, I got this-  

11. (a) The two sides of a triangle are 15 m and 20 m and the perimeter of the triangle is 60 m.

Find the area of the triangle.

15*20=300

80π/3 or about 83.775

step-by-step explanation:

since a cone is 1/3 of a cylinder, we need to find the base's area. since area = πr^2, we get 16π. then, multiplying this by 5, we get 80π. dividing by 3, since the cone's volume is 1/3 of that of a cylinder's, we get 80π/3.

hope this !