Ten years ago, scientists predicted that the animal z would

Question

Ten years ago, scientists predicted that the animal z would become extinct in t years. What is t?

(1) Animal z became extinct 4 years ago.

(2) If the scientists had extended their extinction prediction for animal z by 3 years, their prediction would have been incorrect by 2 years.

Bunuel · Accepted Answer

Ten years ago, scientists predicted that the animal z would become extinct in t years. What is t?

(1) Animal z became extinct 4 years ago. The only thing we can get from this statement is when animal z  actually extincted : 4 years ago or 6 years after the prediction. Not sufficient.

(2) If the scientists had extended their extinction prediction for animal z by 3 years, their prediction would have been incorrect by 2 years. Also not sufficient: t+3=actual extinction +/- 2.

(1)+(2) Animals extincted 6 years after the prediction: t+3=6-2 --> t=1 OR t+3=6+2 --> t=5. Two answers, not sufficient.

Answer: E.

IanStewart · Answer

From S1 we learn that the animal became extinct 6 years after the scientists made their prediction. Of course, we have no info about t, so this is not sufficient. Similarly S2 is not sufficient, since we have no info about when the animal actually became extinct.

Combining the two Statements, we know that if we add three to t, the value we get will be two away from the correct value, which is, from Statement 1, six. We do not, however, know if it will be two above or two below the correct value, so we will get two different possible values for t. That is, the scientists may have predicted the animal would become extinct in 1 year; adding three, we are off by two from the correct value of 6. Or, they may have predicted the animal would become extinct in 5 years; again, adding three, we are off by two from the correct value of 6. The answer is E.

I'm curious where the question is from; it's a bit different from other questions I've seen.

alexBLR · Answer

It is from the MGMAT Question Bank.

gurpreetsingh · Answer

From S1 we get it got extincted 6 years after the prediction. then t =6? they are just asking after how many years of prediction it will be extincted.
Pls correct me where m wrong

alexBLR · Answer

I fall into the same trap and assumed that sientists' prediction is acurate. However, in this case the sientists' prediction for time of extinction is not necessarily equal to the time of actual animal extinction

gurpreetsingh · Answer

oh..haha....sahi

jeeteshsingh · Answer

This question is DS + CR mixed! :maniac

vscid · Answer

its a good question!
+1

suryadasika · Answer

Bunuel, this problem, in my view, is ambiguous in its statement. Is t representing only the scientists' prediction, or the actual time of extinction. And in a math problem , shouldn't we be assuming these to be the same.(and not employ our CR skills)

Bunuel · Answer

Well, common sense says that predictions are not 100% precise. But even if you are confused by the first statement, the second one should help to realize that the predicted extinction date and the actual extinction date are not the same.

EvaJager · Answer

Just my two cents:
I assume that the scientists's prediction is either correct or not, according to the supplied information.

(1) Animal z became extinct 4 years ago or 6 years after the scientists's prediction. Nothing stated about the accuracy of the prediction.
Not sufficient.

(2) In contrast to (1), here we have explicitly stated that t + 3 would be incorrect by 2 years. It means that animal z became extinct in t + 1 years and  t + 1 \leq10  or  t\leq9  because we have already witnessed the extinction.
Not sufficient.

(1) and (2) together:
Scientists predicted t years, but in fact the extinction occurred after t+1 years. We know for sure that this happened 4 years ago or 6 years after the scientists's prediction. This means t + 1= 6 or t = 5.
Sufficient.

Answer C

Bunuel · Answer

Both t=1 and t=5 satisfy the statements. So, the answer is E.

EvaJager · Answer

Oops! I missed the -2 possibility...

ssriva2 · Answer

Hi  Bunuel ,
Initially I choose A.Then after analysis,I found that in question scientist predicted that the animal z "would" become extinct in t years.Would is assumption or uncertainty whereas in answer it is given that animal became extinct 4 years ago(certainty).
Is this the right logic to rule out A?

felippemed · Answer

here is my two cents!

anairamitch1804 · Answer

The question does not ask for the actual number of years ago that animal z became extinct. Instead it asks for t, the number of years scientists predicted it would take for animal z to become extinct.

(1) INSUFFICIENT: This tells us that animal z became extinct 4 years ago but it does not provide information about t.

(2) INSUFFICIENT: This provides a relationship between the predicted time of extinction time and the actual time of extinction but does not provide any actual values for either.

(1) AND (2) INSUFFICIENT: The easiest way to approach this problem is to imagine a time line from 0 to 10. The scientists made their prediction 10 years ago, or at 0 years.

From statement (1) we know that animal z became extinct 4 years ago, or at 6 years.

From statement (2) we know that if the scientists had extended their prediction by 3 years they would have been incorrect by 2 years. The key to this question is to realize that "incorrect by 2 years" could mean 2 years in either direction: 6 + 2 = 8 years or 6 – 2 = 4 years.

From here, we can write two simple equations:

t + 3 = 8 OR t + 3 = 4 
t = 5 t = 1

This gives us two different values for t, which means that (1) and (2) together are not sufficient to come up with one definitive value for t. The correct answer is E.

AD2GMAT · Answer

I have done the same silly mistake twice in this question

. "Actually extinct" v/s "extinct" . Could anyone help me to improve on such things - it would be a great help.

ccooley · Answer

Can you elaborate a little bit on what you mean by this? If you could write out your solution (including where you went wrong), I'd be able to help.

bumpbot · Answer

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Ten years ago, scientists predicted that the animal z would

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