Multiply:

(i) $3 \sqrt{5} \times 2 \sqrt{5}=3 \times 2 \times \sqrt{5} \times \sqrt{5}=6 \times 5=30$

(ii) $6 \sqrt{15} \times 4 \sqrt{3}=6 \times 4 \times \sqrt{5} \times \sqrt{3} \times \sqrt{3}=24 \times 3 \times \sqrt{5}=72 \sqrt{5}$

(iii) $2 \sqrt{6} \times 3 \sqrt{3}=2 \times 3 \times \sqrt{2} \times \sqrt{3} \times \sqrt{3}=6 \times 3 \times \sqrt{2}=18 \sqrt{2}$

(iv) $3 \sqrt{8} \times 3 \sqrt{2}=3 \times 3 \times \sqrt{2} \times \sqrt{2} \times \sqrt{2} \times \sqrt{2}=9 \times 4=36$

(v) $\sqrt{10} \times \sqrt{40}=\sqrt{2} \times \sqrt{5} \times \sqrt{2} \times \sqrt{2} \times \sqrt{2} \times \sqrt{5}=\sqrt{2} \times \sqrt{2} \times \sqrt{2} \times \sqrt{2} \times \sqrt{5} \times \sqrt{5}=2 \times 2 \times 5=20$

(vi) $3 \sqrt{28} \times 2 \sqrt{7}=6 \sqrt{7 \times 4} \times \sqrt{7}=6 \times 7 \times \sqrt{4}=42 \times 2=84$