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Suppose you must take the bus to school. The probability that you will have to wait for the bus is 0.25. If you don’t have to wait for the bus the commute takes 20 minutes, but it you must wait for the bus, the commute takes 30 minutes.

Find the standard deviation. 

Round your answer to 2 decimal places.


On May 11, 2013 at 9:30 PM, the probability that moderate seismic activity (one moderate earthquake) would occur in the next 48 hours in Iran was about 21.42%. Suppose you make a bet that a moderate earthquake will occur in Iran during this period. If you win the bet, you win $50. If you lose the bet, you pay $20. Let X = the amount of profit from a bet.

What is the standard deviation of X?  

Round your answer to 3 decimal places.


A hospital researcher is interested in the number of times the average post-op patient will ring the nurse during a 12-hour shift. For a random sample of 50 patients, the following information was obtained. What is the standard deviation? 





Discuss the factors that affect the adoption of new irrigation technologies
Balance the given redox reaction
Bi (OH)3 + SnO2
A 1 M solution of Cu(NO3)2 is placed in a beaker with a strip of Cu metal. A 1M solution of SnSO4 is placed in a second beaker with a strip of Sn metal. A salt bridge connects two beakers and wires to a voltmeter link the two metal electrodes. [ Hint: Charge of nitrate anion is (-1); Charge of Sulfate ion is (-2)]

What is the emf generated by the cell under standard conditions?
A 1 M solution of Cu(NO3)2 is placed in a beaker with a strip of Cu metal. A 1M solution of SnSO4 is placed in a second beaker with a strip of Sn metal. A salt bridge connects two beakers and wires to a voltmeter link the two metal electrodes. [ Hint: Charge of nitrate anion is (-1); Charge of Sulfate ion is (-2)]

Write the equation for the overall cell reaction
A 1 M solution of Cu(NO3)2 is placed in a beaker with a strip of Cu metal. A 1M solution of SnSO4 is placed in a second beaker with a strip of Sn metal. A salt bridge connects two beakers and wires to a voltmeter link the two metal electrodes. [ Hint: Charge of nitrate anion is (-1); Charge of Sulfate ion is (-2)]

Which electrode gains mass and which loses mass as the cell reaction proceeds?
A 1 M solution of Cu(NO3)2 is placed in a beaker with a strip of Cu metal. A 1M solution of SnSO4 is placed in a second beaker with a strip of Sn metal. A salt bridge connects two beakers and wires to a voltmeter link the two metal electrodes. [ Hint: Charge of nitrate anion is (-1); Charge of Sulfate ion is (-2)]

Which electrode serves as the anode and which as the cathode?
Identify X in the following nuclear equation: Show your solution.
78/33 As -> 0/-1 B + X