What is the density if the length is 2.5 cm the volume 15.6 cm and the mass is 145 g

Two sides of a triangle mesure 20cm and 30cm. what is the measure of the third side

Find the perimeter of the triangle with vertices  d(3, 4),  e(8, 7), and  f(5, 9). do not round before calculating the perimeter. after calculating the perimeter, round your answer to the nearest tenth.  

Cone a has a surface area of 384 ft2 and cone b has a surface area of 96 ft? . what is the ratio of their volume?