Final answer:
To find the probability of picking two bills of different denominations from a wallet containing 7 $5 bills and 3 $20 bills, we can use combinations. The probability is 7/15 or approximately 0.467.
Step-by-step explanation:
In this problem, we are asked to pick two bills from a wallet containing 7 $5 bills and 3 $20 bills, without replacement. To find the probability of picking two bills of different denominations, we can use the concept of combinations.
The total number of ways to pick two bills from a wallet containing 10 bills is given by the combination formula C(10, 2) = 45. The number of ways to pick one $5 bill and one $20 bill is given by C(7, 1) * C(3, 1) = 21. Therefore, the probability of picking two bills of different denominations is 21/45, which simplifies to 7/15 or approximately 0.467.