UPSC CDS Math Volume and Surface Area Questions

Volume of the cone when triangle is revolved about longer leg$=\;\frac{1}{3}\pi \times 15^{2} \times 20$Volume of the cone when triangle is revolved about shorter leg$=\;\frac{1}{3}\pi \times 20^{2} \times 15$$=\;\frac{1}{3}\times 3.14 \times 20^{2} \times 15 = 6280\,\mathrm{cm}^{3}$Hence, statement 1 is incorrect. Volume of the cone when triangle is revolved about longer leg + Volume of the cone when triangle is revolved about shorter leg$=4710+6280=10990\,\mathrm{cm}^{3}$ Volume of the double cone when triangle is revolved about the hypotenuse $=3768\,\mathrm{cm}^{3}$