Arranging four subjects and six periods

Question

Question: How many ways are there to arrange four subjects and six periods in a day if two subjects are taught in two periods and remaining two periods for another two different subject.

Here we can arrange this as 6P4. But I don't understand about the following question part,

"two subjects are taught in two periods and remaining two periods for another two different subject"

Answer 1

I think this question wants you to imagine yourself as a teacher who is scheduled to teach 6 periods, 2 periods English, 2 Math, 1 History and 1 Geography

potential schedules could be

EMGHEM or EEMMGH

• Number of ways to schedule English is $\binom 62$
• for each of these possibilities there are $\binom 42$ways to schedule Math
• for each of the above possibilities there are $\binom 21$ways to schedule Geography
• for each of the above possibilities there are $\binom 11$ways to schedule History

So total # of schedules in $$ \binom 62 \binom 42 \binom 21 \binom 11 $$

which is the same as $$\frac{6!}{2!2!}$$