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The ph level of a blueberry is 3.1 what is the hydrogen-ion concentration [h+] for the blueberry

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

At noon a tank contained 10cm water. after several hours it contained 7cm of water. what is the percent decrease of water in the tank?