A box contains 16 red, 12 white, and 15 yellow identical marbles. A man picks one marble at a time without replacement. How many times must he pick a marble to be 100% certain of picking at least 3 white marbles?
Concept: Worst-case selection (pigeonhole principle).
Explanation: To ensure 3 white marbles, assume the worst case: pick all non-white first. Non-white marbles: \[ 16 + 15 = 31 \] After picking 31 marbles, there are still 0 white marbles in the worst case. Now pick whites: To guarantee 3 whites: \[ 31 + 3 = 34 \]
A doctor attends five patients in 45 minutes. How many hours he has to work if he has to attend 50 patients?
Mr X works in a call center.Each week,he receives number of calls.The unattended calls are queued in the call center monitoring system.The number of calls that he has to attend at the end of each day can be estimated with the equation T =58-100t,where T is total number of calls left to atend and t is the number of work days in the week.What does the number 58 indicates here?