Answer:
600
Step-by-step explanation:
Pair 1 of pants goes with 40 shirts
Pair 2 of pants goes with 40 shirts
Pair 3 of pants goes with 40 shirts
Pair 4 of pants goes with 40 shirts
Pair 5 of pants goes with 40 shirts
Pair 6 of pants goes with 40 shirts
Pair 7 of pants goes with 40 shirts
Pair 8 of pants goes with 40 shirts
Pair 9 of pants goes with 40 shirts
Pair 10 of pants goes with 40 shirts
Pair 11 of pants goes with 40 shirts
Pair 12 of pants goes with 40 shirts
Pair 13 of pants goes with 40 shirts
Pair 14 of pants goes with 40 shirts
Pair 15 of pants goes with 40 shirts
Add up everything (not including the 1,2,3,4,5,...14,15 pairs of pants because each pair of pants goes with 40 different shirts so u just add up all the 40's) and you would get 600 outfits.
Another simple way of doing this would just be multiplying 40x15