Putting the information in a table makes it easier to solve. We’ll use A for Angie, B for Brenda, T for truth and F (false) for lying.
S
M
T
W
Th
F
S
A
T
F
F
F
T
T
T
B
T
T
T
T
F
F
F
To begin with, there aren’t any days where both of them told the truth and lied the day before, so we know one of them must be lying.
So we have two options, either Angel is lying or Brenda is.
Option 1. Angel is lying.
In order for this to be the case, she needs to be lying today and telling the truth yesterday, so we need two days in a row with T F. And if Brenda is telling the truth, she would need two days with F T. That means we’re looking for two days that have
Angie: T F
Brenda: F T
Option 2. Brenda is lying.
This is just the reverse of the above, so we need to find:
Angie: F T
Brenda: T F
The only day that matches either of the two options is Thursday, and it’s option 2. Brenda is the liar.
1. Each letter represents a different digit from 1 to 9 2. The total of each row is 17. 3. (B × B) + B + F = A 4. C × F = EF (a 2-digit number, not their product)
A + B + C = 17 D + E + F = 17 B2 + B + F = A C × F = EF
To begin with, B has to be a 1 or 2 or else A wouldn’t be a single digit. Plug in B = 2, gives you 6 + F = A, meaning F and A can only be (1,7) or (3,9). To get 17, C would have to be 8 or 6, but those values don’t work for C × F = EF. So B must be 1.
2 + F = A means F and A can be (2,4), (3,5), (4,6), (5,7), (6,8) or (7,9). To get 17 on the top row, the only option that leaves C as a single digit is F = 5 and A = 7.
C × F = EF 9 × 5 = 45, so E = 4 and D = 8 to make the second row equal to 17.
Bill buys three items at the store for exactly $100. The second item costs half as much as the first item, and the third item is half as much as the second.
On a game show there are three closed doors – one hides a car and the other two conceal a goat. The contestant selects a door, which remains closed, and the host, knowing where the car is hidden, reveals a goat behind one of the remaining two doors. The contestant is then given the option to switch doors or stay with the one they originally selected. What should the contestant do to have the best chance of winning the car?
The contestant should switch doors, which doubles the chance of winning the car. Initially there is a 2/3 chance of picking a goat, but once the other goat is revealed, switching to remaining door gives the contestant a better chance of winning the car. This is known as the Monty Hall Problem and can be very unintuitive.
Kevin brings his school supplies to the counter. The cashier rings up his purchase for a total of $1.70. Kevin is puzzled, and says, “I bought 2 pencils at 2 cents each, 5 pencils at 4 cents each and 8 notebooks and 12 sheets of colored paper. I don’t remember the prices of the latter two, but the total can’t be $1.70.”