GMAT Club Olympics 2025 (Day 1): At a wildlife reserve, two tracking

In each session, 16 animals are paired into 8 groups, with 8 dominant and 8 subordinate animals.

Given that 5 animals subordinate in the first session remained subordinate in the second, the other 3 first-session subordinates (8 - 5 = 3) became dominant in the second session.
The second session has 8 dominant spots, filled by these 3+x animals that were dominant in both sessions. Thus, 3 + x = 8, so x = 5.
Answer: (D) 5

Analyzing the data, there were 8 dominant and 8 subordinate animals in session 1

In session 2, 5 remained subordinate, meaning the rest 8 - 5 = 3 became dominant.

This means that the rest of the dominant animals from session 2, 8 - 3 = 5, Should also have been dominant in session 1.

So the Correct answer is, Option D

In first tracking session we have 8 dominant and 8 subordinate animals
In second tracking session, out of 8 subordinate animals from first session, we have 5 again as subordinate
Which means that 3 animals which were dominant in first session are subordinate in second session
Hence we can conclude (8-3) 5 animals were dominant in both sessions

	Session 2 - Dominant	Session 2 - Subordinate	Total
Session 1 - Dominant	5	3	8
Session 1 - Subordinate	3	5	8
Total	8	8	16

There are 16 animals in total, and in each session, 8 are dominant and 8 are subordinate.
We are told that 5 animals were subordinate in both sessions (yellow one). Since 8 animals were subordinate in session 1, the remaining 3 must have been dominant in session 2.
Now, session 2 has 8 dominant animals. 3 of them came from the session 1 subordinates. So the other 5 must be animals that were dominant in both sessions (green one)

So the number of animals that were dominant in both sessions is 5 (D)

Here at first in the first session, there were 8 sub and 8 dom.Then after that in the second session, only 5 were sub. That means 3 of the sub-animals from the first session become dominant in the second session. Which means the rest 5 dom in the second session came from the dominant animals from the first session.Hence the answer is D that is 5.

We are told:

16 animals were observed in two tracking sessions.

In each session, the 16 animals were divided into 8 pairs, and in each pair, one animal is dominant, one is subordinate.

So, in each session:

8 animals = dominant

8 animals = subordinate

We are told:

5 animals were subordinate in both sessions.

We are asked:

How many animals were dominant in both sessions?

🔎 Step-by-step:
Let’s build a table:

(Dominant in Session 2 ; Subordinate in Session 2 ; Row Total)
Dominant in Session 1 ( ? ; ? ; 8)
Subordinate in Session 1 ( ? ; 5 (given) ; 8)
Column Total (8 ; 8 ; 16)

Let’s fill in the 5 subordinate-subordinate spot:

That leaves 3 animals in the subordinate row who were dominant in session 2 (since 8 − 5 = 3)

Now update the table:

(Dominant in Session 2; Subordinate in Session 2;Row Total)
Dominant in Session 1 (x ; y ; 8)
Subordinate in Session 1 (3 ; 5 ; 8)
Column Total (8 ; 8 ; 16)

Now, the dominant in both sessions are in the top-left cell (x).

From column total for Dominant in Session 2:

x + 3 = 8 → x = 5

✅ So, 5 animals were dominant in both sessions.

✅ Final Answer: (D) 5

In both the sessions, there would be 8 dominants and 8 subordinates

Since 5 which were subordinate in the first session was also subordinate in the second, 3 would have become dominant. Accordingly, 3 animals which were dominant in the first session would have become subordinate in the second session.

Therefore, it follows that 5 animals would have been dominant in both the sessions.

Option D

• A = Subordinate in session 1 = 8 animals
• B = Subordinate in session 2 = 8
• Subordinate in both sessions = A \( \cap \) B = 5 animals

Therefore, Subordinate in either of the two sessions =
|A \( \cup \) B| = |A| + |B| - |A \( \cap \)B| = 8 + 8 - 5 = 11

Therefore, subordinate in neither of the sessions = 16 - 11= 5 (option D)

Let’s say we have two sets of tagged animals: abcdefgh and pqrstuvw. We form 8 pairs: (a, p), (b, q), ..., (h, w).

Now, assume that animals a to e are always in subordinate roles across both sessions.

Session 1:
Dominant: p, q, r, s, t, u, v, w
Subordinate: a, b, c, d, e, f, g, h

Session 2:
Dominant: f, g, h, p, q, r, s, t
Subordinate: a, b, c, d, e, u, v, w

In both sessions, five animals (a to e) consistently remain subordinate. The remaining three subordinate positions are filled by rotating the other animals. No matter how you rearrange the remaining animals, there will always be five animals who are dominant in both sessions.

answer is D : 5

In session 1 there are 8 dominant and 8 subordinates. Are there in session 2, there 5 who are subordinate. and the remaining three has become dominant. like wise three of them have become subordinate and 5 of them have beocme dominant.

Draw a table and solve, ans = 5

Of the animals that were subordinate in the first session, 5 were also subordinate in the second session, meaning there were another 3 dominant within the same group. That means of the 8 animals that were dominant in the 1st session, there would be another 5 that are dominant in order to have a total of 8 dominant animals within the second session.

Answer: D

There are a total 16 Animals.

Both sessions have 8 subordinates and 8 dominants.

We’re told: among the 8 animals subordinate in Session 1, 5 were also subordinate in Session 2. That means 3 of the Session 1 subordinates became dominant in Session 2.

Session 2 requires a total of 8 dominant players. So, those are:
[*]The 3 who switched from subordinate → dominant, and
[*]5 who stayed dominant from Session 1 to Session 2.


So, 5 remain dominant in both sessions.

D)5

D - Dominant
S - Subordinate

1st Session
8 D and 8 S

now, 5 of the S stayed S in the 2nd Session too.
That means of the 8 Dominants, 3 of them will now become Subordinate. Hence, only 5 stayed dominant from the 1st session into the second session. Hence, 5 (D).

Attached image contain my solution.

I assumed 16 animals and based on the data in question I created the following cases.

The correct answer according to me is 5

D D D D D 0 0 0
S S S S S S S S

D D D D D S S S
S S S S S 0 0 0


ANSWER IS 5 we assume the orange present d, and there is 3 space for d to swich with s, so there are 5 orange left ,means it will still have 5 d in both round

Each session has 8 dominant and 8 subordinate.

As the 5 subordinates are common between both the sessions , 3 subordinate have moved from subordinate to dominate in second session, the remaining are dominant in both the sessions.

8 - 3 = 5 wildlife are dominant in both the sessions.

Option D