How many different boat parties of 8 consisting of 5 boys and 3 girls can be

Number of ways of choosing 5 boys out of 20 boys $={ }^{20} \mathrm{C}_{5}$

$=\frac{20 !}{5 ! \times(20-5) !}$

$=\frac{20 !}{5 ! \times 15 !}$

$=19 \times 17 \times 16 \times 3=15,504$

Number of ways of choosing 3 girls out of 10 girls $={ }^{10} \mathrm{C}_{3}$

$=\frac{10 !}{3 ! \times(10-3) !}$

$=\frac{10 !}{3 ! \times 7 !}$

$=15 \times 8=120$

Total number of ways $=120 \times 15,504=1,860,480$

OR

Total number of ways $={ }^{20} \mathrm{C}_{5} \times{ }^{10} \mathrm{C}_{3}$