One pipe can fill a pool in 10 hours. another pipe can fill the pool in 30 hours. how long would it take them to fill the pool if they were working together?

Suppose you are choosing a 6-digit personal access code. this code is made up of 4 digits chosen from 1 to 9, followed by 2 letters chosen from a to z. any of these digits or letters can be repeated. find the total number of personal access codes that can be formed. 492,804 341,172 39,917,124 4,435,236

Why is causation so much more difficult to prove than correlation?

Which expression represents the total perimeter of her sandwich, and if x = 1.2, what is the approximate length of the crust?