Answer :
Let's solve the problem step-by-step.
### Step 1: Identify the animals each person cannot study
1. David is studying a mammal
- Mammals: Elephant, Giraffe, Dolphin
2. Ping is not studying a mammal
- Non-mammals: Sailfish
3. Mandy's animal can be found in the ocean
- Ocean animals: Sailfish, Dolphin
4. Alan's animal is slower than the one David is studying
### Step 2: Narrow down options for Mandy and David
1. Mandy can study Sailfish or Dolphin (both are ocean animals)
2. Let’s consider two cases:
- Case 1: Mandy studies Sailfish
- Case 2: Mandy studies Dolphin
#### Case 1: Mandy studies Sailfish
If Mandy studies Sailfish:
- David must study a mammal: Elephant, Giraffe, Dolphin
- Alan’s animal must be slower than David’s animal:
- Elephant: 25 mph
- Giraffe: 32 mph
- Dolphin: 30 mph
To satisfy Alan’s condition, both Dolphin and Giraffe are faster than at least one mammal:
- If David studies Dolphin (30 mph), only Elephant (25 mph) is slower
- If David studies Giraffe (32 mph), only Elephant again is slower
Therefore, David studies Dolphin and Alan studies Elephant.
#### Case 2: Mandy studies Dolphin
If Mandy studies Dolphin:
- David’s remaining mammals: Elephant, Giraffe
- Alan’s animal must be slower than David’s animal:
- David studying Elephant (25 mph): No animal slower
- David studying Giraffe (32 mph): Elephant (25 mph) is slower
- If David studies Giraffe (32 mph), Alan must study Elephant (25 mph)
Thus, this case also leads to Alan studying Elephant.
### Step 3: Final answer
From the analysis of both cases, the only consistent solution is that Alan is studying the Elephant.
So, Alan is studying:
- Animal: Elephant
- Speed: 25 mph
### Step 1: Identify the animals each person cannot study
1. David is studying a mammal
- Mammals: Elephant, Giraffe, Dolphin
2. Ping is not studying a mammal
- Non-mammals: Sailfish
3. Mandy's animal can be found in the ocean
- Ocean animals: Sailfish, Dolphin
4. Alan's animal is slower than the one David is studying
### Step 2: Narrow down options for Mandy and David
1. Mandy can study Sailfish or Dolphin (both are ocean animals)
2. Let’s consider two cases:
- Case 1: Mandy studies Sailfish
- Case 2: Mandy studies Dolphin
#### Case 1: Mandy studies Sailfish
If Mandy studies Sailfish:
- David must study a mammal: Elephant, Giraffe, Dolphin
- Alan’s animal must be slower than David’s animal:
- Elephant: 25 mph
- Giraffe: 32 mph
- Dolphin: 30 mph
To satisfy Alan’s condition, both Dolphin and Giraffe are faster than at least one mammal:
- If David studies Dolphin (30 mph), only Elephant (25 mph) is slower
- If David studies Giraffe (32 mph), only Elephant again is slower
Therefore, David studies Dolphin and Alan studies Elephant.
#### Case 2: Mandy studies Dolphin
If Mandy studies Dolphin:
- David’s remaining mammals: Elephant, Giraffe
- Alan’s animal must be slower than David’s animal:
- David studying Elephant (25 mph): No animal slower
- David studying Giraffe (32 mph): Elephant (25 mph) is slower
- If David studies Giraffe (32 mph), Alan must study Elephant (25 mph)
Thus, this case also leads to Alan studying Elephant.
### Step 3: Final answer
From the analysis of both cases, the only consistent solution is that Alan is studying the Elephant.
So, Alan is studying:
- Animal: Elephant
- Speed: 25 mph