Question

5 countries president and prime minister went for a summit. If all 5 prime ministers shake hand to president at random, in how many ways they can shake hand if all 5 PMs shake hand only to their country president only.

• A. 21
• B. 1
• C. 2
• D. 44

Answer 1

The correct option is B

1

Let's say PMs are $p{m}_1,p{m}_2,p{m}_3,p{m}_{4}andp{m}_5$
Presidents are $p_1,p_2,p_3,p_{4}and{p}_5$
For all 5 PMs to shake hand to their country president only
pm1 shakes hand with $p_1$
pm2 shakes hand with $p_2$
pm3 shakes hand with $p_3$
pm4 shakes hand with $p_4$
pm5 shakes hand with $p_5$
This can be done only 1 way.