1/183

[K_I_R_E_E_K]

1/1 means 1 chance in 1 total, so that's 100%

1/2 means 1 chance in 2, it's like fliping a coin, so it's 50%

Now you see some drop rates like 1/117, all you need is to imagine a bag that contains 116 black balls and 1 white ball, if you try to take out the white ball the chances will be 1/117.
Same thing is aplied here, keep in mind that the drop rate remains the same no matter the amout of times you try, so it's 1/117 every single time.
The more enemys (the same enemy) you kill, the more oportunities you have to get the item, that's why some ppl do specific quests because they know certain quests have a high amount of that enemy.