The first step is to figure out what the coins are. Since you have 67 cents - at least 2 coins must be pennies. Now, what about the other 4? Well, at least one coin must be a Quarter, because you can't have 4 dimes - that would only equal 42 cents. But wait! If you have only 1 Quarter and 2 pennies - you still can't get to 67 cents with just 3 dimes - so therefore, there must be 2 Quarters!

Now it's easy: 2 Quarters + 2 Pennies = 52 cents. You only need 15 more cents, and you only have 2 coins to do it. The only way that's gonna happen is with a dime and a nickle. So, let's recap:
2 Quarters
1 Dime
1 Nickel
2 Pennies

Now let's calculate the probability:
The chance of drawing a nickel is 1/6: 16.666667%
The chane of *then* drawing a quarter is NOT 2/6 it's 2/5 because the nickel is not replaced: 40%

Now all you have to do is multiply these 2 percentages together (convert back to decimals first):
0.1666667 * 0.4 = 6.67% And that's your answer!

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