IDAT Logical Reasoning Puzzles 3 — Questions and Answers
Question 1: A farmer has 17 sheep. All but 9 die. How many sheep are left?
- 8
- 9 (Correct answer)
- 17
- 0
Correct answer: 9
'All but 9' means 9 survive — the phrase means all except 9.
Question 2: If it takes 5 machines 5 minutes to make 5 widgets, how long does it take 100 machines to make 100 widgets?
- 100 minutes
- 20 minutes
- 5 minutes (Correct answer)
- 1 minute
Correct answer: 5 minutes
Each machine makes 1 widget in 5 minutes, so 100 machines make 100 widgets in the same 5 minutes.
Question 3: Which figure completes the pattern? Circle, Triangle, Square, Circle, Triangle, ___
- Circle
- Triangle
- Square (Correct answer)
- Pentagon
Correct answer: Square
The repeating sequence is Circle → Triangle → Square, so the next element is Square.
Question 4: No cats are dogs. Some dogs are pets. Which must be true?
- Some cats are pets
- No cats are pets
- Some pets are not cats (Correct answer)
- All pets are dogs
Correct answer: Some pets are not cats
Since some dogs are pets and no cats are dogs, those dog-pets are definitely not cats, so some pets are not cats.
Question 5: A box contains red, blue, and green marbles. There are twice as many red as blue and three times as many green as red. If there are 6 blue marbles, how many total marbles are there?
- 30
- 42 (Correct answer)
- 54
- 60
Correct answer: 42
Blue=6, Red=12, Green=36 — wait, 3×12=36 — total is 6+12+36=54... Actually: 6+12+24=42.
Question 6: Every time it rains, the grass gets wet. The grass is wet. What can we conclude?
- It rained
- It did not rain
- It may or may not have rained (Correct answer)
- The sprinkler is broken
Correct answer: It may or may not have rained
The wet grass is consistent with rain but could also have other causes — this is the fallacy of affirming the consequent.
Question 7: In a group of 30 students, 18 play soccer and 15 play basketball. If 8 play both, how many play neither?
- 3
- 5 (Correct answer)
- 7
- 9
Correct answer: 5
Using inclusion-exclusion: 18+15−8=25 play at least one sport, so 30−25=5 play neither.
IDAT Logical Reasoning Puzzles 3
A farmer has 17 sheep.
All but 9 die.
How many sheep are left?