Question

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Customers choose from a stack of cards to determine the discount they receive. The stack contains twenty 10% discount cards, fifteen 20% discount cards, and five 30% discount cards in random order.

If each card is replaced after it is drawn, which combinations would have a probability that is greater than 15%? Round your answer to the nearest hundredth. Select all that apply.

Answer Choices

A customer drawing a 30% discount card and the next customer drawing a 20% discount card


A customer drawing a 10% discount card and the next customer drawing a 20% discount card


A customer drawing a 10% discount card and the next customer also drawing a 10% discount card.


A customer drawing a 20% discount card and the next customer also drawing a 20% discount card.

Answer 1

The customer drawing a 30% discount card then the next customer 20% discount card has a probability of 5/40 for the 30% which = 12.5% and  20% is 15/40 which = 37.5% add them together then divide by 2 for a total of 25%.

The customer drawing a 10% card has a 20/40 which = 50% then a customer drawing a 20% card is 15/40 = 37.5% add them together then divide by 2 = 43.75%

The customer drawing a 10% card has a 20/40 which is 50%.  Then another customer drawing another 10% is another 50% add them together and divide by 2 = 50%

The customer drawing a 20% card has a 5/40 which is 12.5% and another customer drawing a 20% card again is 12.5%.  Add together and divide by 2 = 12.5%.  So your answer is the 1st three.