CAT 2018 Question Paper | CAT LR DI

CAT Questions

Here is a question from slot 1 CAT 2018 where you need to point out the fallacious choice among the given 4 choices. The Petrol Pump-based puzzle has been a demanding set due to its large and highly complex data. If you feel such sets are not your cup of tea, better to omit it on the d-day! Puzzle selection is crucial to score high in the DILR section. So practice how to choose puzzles wisely from CAT previous year paper and nail your CAT EXAM preparation

CAT DILR : CAT 2018 Question Paper Slot 1

Set 6 : Petrol Pumps

Fuel contamination levels at each of 20 petrol pumps P1, P2, …, P20 were recorded as either high, medium, or low.

1. Contamination levels at three pumps among P1 – P5 were recorded as high.
2. P6 was the only pump among P1 – P10 where the contamination level was recorded as low.
3. P7 and P8 were the only two consecutively numbered pumps where the same levels of contamination were recorded.
4. High contamination levels were not recorded at any of the pumps P16 – P20.
5. The number of pumps where high contamination levels were recorded was twice the number of pumps where low contamination levels were recorded.

Question 4 : If contamination level at P15 was recorded as medium, then which of the following MUST be FALSE?

1. Contamination levels at P11 and P16 were recorded as the same.
2. Contamination levels at P10 and P14 were recorded as the same.
3. Contamination level at P14 was recorded to be higher than that at P15.
4. Contamination levels at P13 and P17 were recorded as the same.

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Video Explanation

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Explanatory Answer

Method of solving this CAT Question on CAT DILR

We know that three of P1 to P5 are recorded as High. This means the other two should be M. So, let us fill this data in.

P7 and P8 are both same, so both could be H or both M. Let us try both. We put P7 and P8 in, P9 and P10 get filled automatically.
Let us fill in the totals as well.

The number of pumps where high contamination levels were recorded was twice the number of pumps where low contamination levels were recorded.
So, of the number of low contaminations were x, then the number of high contaminations would be 2x.
H + L = 3x {3, 6, 9, 12, 15, or 18} or, M should be from {2, 5, 8, 11, 14, 17}
L + H is at least 5 so M cannot be 14 or 17. M cannot be 2 either. So, we can have M to be 5, 8 or 11.
So, we can have H, M, L to be {10, 5, 5} or {8, 8, 4} or {6, 11, 3}
There is no H in the P16 to P20 range, so total H cannot be 10. So, H, M, L being {10, 5, 5} can be ruled out.
So, we can have H, M, L to be {8, 8, 4} or {6, 11, 3}.
We cannot have more than 5 M’s in the range from P16 to P20.
So, we now know that {6, 11, 3} is also ruled out. So H, M, L has to be {8, 8, 4}.

We know that in the first 10 pipes we could have has H, M, L could have been {6, 3, 1} or {4, 5, 1}
So, H, M, L for the last 10 should be {2, 5, 3} or {4, 3, 3}. Since there is no H in the first 5 pipes, we cannot have 4 H in the P16 to P20 range.
So, we need to have only {6, 3, 1} in the first range.

The last 10 pipes should have H, M, L to be {2, 5, 3}.
High contamination levels were not recorded at any of the pumps P16 – P20. So, the last 5 should be either MLMLM or LMLML.
If the last 5 were LMLML, then we would not have one more L for P11 to P15. So, P11 to P15 should be MHMHM. Now, let us fine-tune this.

We know that P11 cannot be H otherwise P10 and P11 would be H.
So, we need to accommodate 2 H’s in the P12 to P15 range.
We could have them at P12 and P14, P12 and P15 and P13 and P15.

If P15 were not H, it has to be L. So, we can fill the first column completely.

P15 was recorded as maximum. This eliminates 3 possibilities.

From the table we can see that, except choice A everything is true and therefore our answer is Choice A.

The question is "If contamination level at P15 was recorded as medium, then which of the following MUST be FALSE?"

Hence, the answer is Contamination levels at P11 and P16 were recorded as the same.

Choice A is the correct answer.