Question

Charlie wishes to visit a friend's house. From his residence to downtown Chicago, he can take one of four bus lines or seven train lines. From there, he can take one of three bus or five rail services to his friend's house. How many options does he have for getting to his friend's house?

• A. $99$
• B. $66$
• C. $88$
• D. $77$

Answer 1

The correct option is C $88$

Since Charlie can either take a bus or a train downtown, he has $4+7=11$ ways to head downtown (Rule of sum).

After which, he can either take a bus or a train to his friend's house, and hence he has another $3+5=8$ ways to head to his friend's house (Rule of sum).

Thus in total, he has $8\times 11=88$ ways to head from his home to his friend's house (Rule of product).