SET UP:
-3 Groomers: Lisa, Mario, and Nancy (L.M.N)
-Schedule: 1-hour appointment slots available for
each groomer at 8, 9 and 10
-7 animals with appointments: 4 poodles (p.p.p.p) 2 terriers (t.t), and 1 westie (w)
*Note: though it doesn't really matter in this game, when given 2 variables, (like
animals and groomers,) I usually prefer to make one set of variables upper case and
another lower case for easier distinction.
-No more than one animal is assigned to any time slot.
RESTRICTIONS/RULES: 1. Lisa grooms more animals than any other groomer
2. At least one poodle is groomed before any terrier is groomed.
3. Each groomer grooms at least two different types of animals.
4. Nancy grooms a poodle at 10 am.
5. No terrier can be groomed during the same hour that a poodle is groomed.
6. Mario does not groom a poodle first.1. L grooms more animals than any other groomer There are 3 time slots available for each groomer, so 9 slots available in total. Anytime I see a grouping game, I do the following: I put each item to be placed in each slot available and see how many slots are left. In other words, subtract the number of items to be placed by the slots available, in this case 9 minus 7. So we now know that there will be 2 slots left empty.
L _____ _____ _____
M _____ _____ _____
N _____ _____ _____
__8__ __9__ __10__
After drawing a quick sketch of the three times (8, 9, and 10) and the groomers along the Y-axis, I start to play with the numbers. If L grooms 1 animal, M and N cannot groom any, and 6 sad animals would be left dirty. So L MUST groom more than 1.
If L grooms 2, that leaves 5 animals. If 5 were left, either M or N would need to groom 3, which would contradict the rule that L grooms MORE than EITHER M or N. So, L must groom 3 animals, leaving 4 to be groomed. M and N must each groom 2, because, as stated earlier, each must groom fewer than L (fewer than 3). Now we can also see that L must groom an animal in each of the three time slots, (8, 9, AND 10) since no more than one animal can fill a time slot for an individual groomer.
L _____ _____ _____ ALL must be filled
M _____ _____ _____ 2 must be filled
N _____ _____ _____ 2 must be filled
__8__ __9__ __10__
2. At least one poodle is groomed before any terrier is groomed Because there are only 3 times to choose from, (8, 9, or 10,) and a poodle must be groomed BEFORE any terrier, that no terrier may be groomed in an eight o clock time slot. So we should place a "t" under the 8 hour and cross it out. This leaves 6 slots available (3 nine slots and 3 ten slots) to place the 2 terriers.
L _____ _____ _____ ALL must be filled
M _____ _____ _____ 2 must be filled
N _____ _____ _____ 2 must be filled
__8__ __9__ __10__
_-t-_
3. Each groomer grooms at least two different types of animalsThis rule, in conjunction with the first rule that allowed us to infer that Lisa would groom 3 animals, (note, it did NOT say 3 DIFFERENT animals,) and M and N would each groom 2, that at exactly 2 poodles will be groomed by L and that M and N will each groom exactly one poodle. L cannot groom 3 poodles, because then she would not satisfy this rule that each groomer will groom at least two different types of animal. That leaves 2 poodles left over, and neither M nor N may groom 2 poodles, because then they would not meet this criterion either.
4. Nancy grooms a poodle at 10 amNow we can cross out one of our four poodles and place a "p" in Nancy’s 10 o’clock time slot.
ppp -p-
tt
w
L _____ _____ _____ ALL must be filled
M _____ _____ _____ 2 must be filled
N _____ _____ __p___ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
5. No terrier can be groomed during the same hour that a poodle is groomed __t, t__
L _____ _____ _____ ALL must be filled
M _____ _____ _____ 2 must be filled
N _____ _____ __p___ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
Now we can see that both terriers must be groomed in the 9 o’clock hour because no terrier can be groomed in either the 8 or the 10 o’clock hours. Jot the 2 "t"s above the 9 o'clock slot, not indicating which spots they will fall into.
We can also infer from this rule that no poodle will be groomed in the 9 o’clock hour since if it were, no terrier would be allowed there.
6. Mario does not groom a poodle first. __t, t__
L _____ _____ _____ ALL must be filled
M _X/w_ _____ _____ 2 must be filled
N _____ _____ __p___ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
At the very least, we know that Mario may not groom a poodle in the 8 o’clock hour. This does not tell us, however, that he grooms ANY animal in the 8 o’clock hour. Because Mario grooms only 2 animals, his first animal could be groomed at either 8 or 9. So, because I can't appropriately format my diagram to indicate a crossed out "p" under M's 8 time slot, I'll place X/w in that space to represent it may be empty (X) or have a westie
Because M and N are only allowed to groom 1 poodle each, we are left with 2 more poodles that must be groomed by L. Because no poodle may be groomed in any 9 o'clock hour, L must groom a poodle in both the 8 and 10 o'clock hours. Because she must fill all of the 3 hours, she must groom either a westie or a terrier in the 9 o'vlock hour, as indicated below:
__t, t__
L __p___ __t/w_ __p__ ALL must be filled
M _X/w_ _____ _____ 2 must be filled
N _____ _____ __p__ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
Before moving on to the questions, note that M MUST groom a poodle in either the 9 or 10 o'clock hour, whichever is his second (and last) appointment.
MOVING ON TO THE QUESTIONS...
1. Which one of the following must be true?X(A) Mario is assigned exactly one animal.
X(B) Nancy is assigned exactly one animal.
X(C) Lisa is assigned exactly two animals.
(D) Mario is assigned exactly two animals.X(E) Nancy is assigned exactly three animals.
We know that both Mario AND Nancy must EACH groom exactly 2 animals, and Lisa grooms exactly 3, so A, B, and C can immediately be eliminated.
At this point, we move on to D and see that it is correct. In a test, at this point we would bubble in answer choice D and move on. For the sake of clarity, though, we'll examine E as well. E must be false for the same reason A, B, and C were false.
2. Which one of the following must be false?(A) Lisa grooms the westie.
(B) Nancy grooms two of the poodles.(C) At least one of the terriers is groomed at 9 am.
(D) The westie is groomed before either of the terriers.
(E) Mario’s last appointment of the day is a poodle.
Because this is a "which must be false" question, if I don't see a clear answer popping out at first glance, I'll save it until after I've finished the questions starting with the word "If".
In this case, I start with A and am not initially sure whether or not it's correct, so I move on to B. As we inferred earlier, N only grooms 2 animals, and each groomer must groom at least 2 different animals. If N grooms 2 poodles, we will contradict these rules, so it MUST be false. Select B and move on!
3. If the westie is groomed at 9 am, which one of the following must be true?On "If" questions, always start by making a quick sketch of the diagram with the conditions stated included. In this case, place a "w" above the 9 o'clock column
Because we know that both terriers must also be groomed in the 9 o'clock hour, we'll include them as well. Clearly, there are no remaining 9 o'clock slots available.
We can now see that each groomer MUST fill a 9 o'clock slot, L must fill EVERY slot, and N fills the 10 o'clock slot with a "p". Because N fills exactly 2 slots, we know that she cannot fill her 8 o'clock slot. Indicate this with an "X," or whatever symbol helps you the most.
After eliminating the "w" and two "t"s that go into the 9 o'clock hour, the only remaining animals are poodles. Because L must fill all of her time slots, she must groom a poodle in both the 8 and 10 o'clock hours.
That leaves an additional poodle to be groomed, and only M can groom it! He isn't allowed to groom a poodle as his first grooming appointment, so he must groom it in his 10 o'clock slot, leaving nothing in his 8 o'clock slot. Now we can move on to the answer choices.
(A) Nancy does not have a grooming appointment at 8 am.Boom. Done. From the sketch we quickly drew, we can see that N may not have an appointment in her 8 o'clock slot. Since this is a "Must Be True" question, this is our answer!
(B) Mario has a grooming appointment at 8 am.
(C) Both terriers are groomed at 10 am.
(D) Mario grooms the westie.
(E) Nancy does not groom a terrier.
__t, t__
L __p__ __t/w_ __p__ ALL must be filled
M __X__ __t/w___ __p__ 2 must be filled
N __X__ __t/w___ __p__ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
4. The schedule of grooming appointments would be completely determined if which one of the following were true?As in question 2, which was a "must be false" question, if I don't see a clear answer popping out at first glance, I'll save it until after I've finished the questions starting with the word "If".
(A) Nancy grooms the westie.
Because N could groom the westie in either the 8 or 9 o'clock time slots, this is an incorrect answer.
(B) Mario grooms the westie.
Same explanation as A
(C) The westie is not groomed at 8 am.
As we can see from question 3, if the westie is groomed in the 9 o'clock hour, we still don't know which of the groomers will groom it. Incorrect answer choice.
(D) Mario’s first appointment is at 9 am.
As in C, we still don't know who grooms two of the terriers and who will groom the westie if this is the case.
(E) Lisa grooms the westie.As this is the final answer choice remaining, it must be correct. Choose it and move on!
__t, t__
L __p___ __w_ __p__ ALL must be filled
M __X__ __t___ __p__ 2 must be filled
N __X___ __t___ __p__ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
5. If Mario grooms a terrier, each of the following could be true EXCEPT:
__t, t__
L __p___ __t/w_ __p__ ALL must be filled
M __X__ __t___ __p___ 2 must be filled
N _?____ __?___ __p__ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
(A) Nancy grooms the westie at 8 am.
Nancy could groom the westie at either 8 or 9 o'clock
(B) Lisa grooms the westie at 9 am.
Incorrect
(C) Mario grooms the westie at 8 am.CORRECT! Since Mario must groom the terrier at 9 o'clock, he must groom a poodle at 10 since his first animal may not be a poodle. He grooms EXACTLY 2 animals, so he's unable to groom
any animal at 8.
(D) Lisa grooms a terrier at 9 am.
(E) Nancy grooms a terrier at 9 am.
6. If the condition that Nancy grooms a poodle at 10 am is replaced with the condition that Nancy grooms the westie at 10 am, and if all other constraints remain in effect, each of the following must be true EXCEPT:
__t, t__
L __p___ __t___ __p__ ALL must be filled
M _X___ __t___ __p___ 2 must be filled
N __w___ __X___ __p__ 2 must be filled
__8__ __9__ __10__
_-t-_ __-t-__
Because M and N each groom 1 poodle exactly, with this new condition, N must groom a poodle at 8, (as no poodle may be groomed in the 9 slots where the two terriers are designated.)
Similarly, M must groom a poodle at 10.
Because M and L are the only groomers available to groom the two terriers in the 9 o'clock slots, they must!
(A) Mario grooms a poodle.
Incorrect, this MUST be true
(B) Nancy grooms a poodle.
Incorrect, this MUST be true
(C) Lisa grooms a terrier.
Incorrect, this MUST be true
(D) Mario grooms a terrier.
Incorrect, this MUST be true
(E) Nancy grooms a terrier.CORRECT! Not only does this not NEED to be true, but it CANNOT be true!
DONE!!!