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Learn the why. Take your time.

18 science, probability and logic questions with answers, explanations and sources.

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What mainly causes Earth’s yearly seasons?

  1. Distance from the Moon
  2. Earth’s axial tilt
  3. Ocean salt
  4. Earth’s size
Answer and explanation

Correct answer: Earth’s axial tilt

The tilt changes how sunlight reaches each hemisphere during the year.

Source / reasoning: NASA · Earth facts ↗

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When it is summer in the Northern Hemisphere, which season is it in the Southern Hemisphere?

  1. Spring
  2. Summer
  3. Autumn
  4. Winter
Answer and explanation

Correct answer: Winter

The hemispheres have opposite seasons because one tilts toward the Sun while the other tilts away.

Source / reasoning: NASA · Earth facts ↗

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Can liquid water evaporate without boiling?

  1. Yes
  2. Only if it freezes first
  3. Only on the Moon
  4. No
Answer and explanation

Correct answer: Yes

Evaporation can happen at the liquid surface below the boiling point.

Source / reasoning: USGS · Evaporation and the water cycle ↗

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During evaporation, liquid water becomes…

  1. Rock
  2. Ice
  3. Water vapour
  4. Salt
Answer and explanation

Correct answer: Water vapour

Evaporation is a change from liquid water to its gaseous form.

Source / reasoning: USGS · Evaporation and the water cycle ↗

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Why does the Moon keep approximately the same face toward Earth?

  1. It never rotates
  2. It rotates once per orbit
  3. It orbits the Sun only
  4. Earth blocks its rotation
Answer and explanation

Correct answer: It rotates once per orbit

The Moon’s rotation and orbit around Earth take the same time. This is synchronous rotation.

Source / reasoning: NASA · Moon facts ↗

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Is the Moon’s far side always dark?

  1. Yes, everywhere
  2. Only in summer
  3. No
  4. Only during a full moon
Answer and explanation

Correct answer: No

Far side means the side facing away from Earth, not a hemisphere permanently without sunlight.

Source / reasoning: NASA · Moon facts ↗

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A fair six-sided die is numbered 1–6. What is the probability of an even number?

  1. 1/6
  2. 1/3
  3. 2/3
  4. 1/2
Answer and explanation

Correct answer: 1/2

The even results are 2, 4 and 6: three of six equally likely outcomes, so 3/6 = 1/2.

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Two independent fair coin tosses: probability of exactly one head?

  1. 1/2
  2. 1/4
  3. 3/4
  4. 1
Answer and explanation

Correct answer: 1/2

HH, HT, TH and TT are equally likely. HT and TH each contain exactly one head: 2/4.

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A bag has 2 red and 3 blue counters. Each counter is equally likely. Chance of drawing red?

  1. 3/5
  2. 1/2
  3. 2/5
  4. 2/3
Answer and explanation

Correct answer: 2/5

There are five counters, and two are red. Count counters, not colour names.

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On a fair die numbered 1–6, how likely is a result greater than 4?

  1. 1/6
  2. 1/3
  3. 1/2
  4. 2/3
Answer and explanation

Correct answer: 1/3

Only 5 and 6 qualify: 2/6 = 1/3. The number 4 is not greater than 4.

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After five heads, what is the chance of heads on the next independent fair coin toss?

  1. 0
  2. 1/6
  3. 1
  4. 1/2
Answer and explanation

Correct answer: 1/2

Independence means earlier tosses do not change this toss. The next head still has probability 1/2.

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A bag has 2 red and 3 blue counters. Remove one red counter. Chance the next randomly drawn counter is red?

  1. 2/5
  2. 1/5
  3. 1/4
  4. 1/2
Answer and explanation

Correct answer: 1/4

One red and three blue remain: one red among four counters. The first counter is not replaced.

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All cards in a box are blue. This card came from that box. What follows?

  1. It is blue
  2. It is round
  3. It is red
  4. It is large
Answer and explanation

Correct answer: It is blue

The rule covers every card in the box. It says nothing about size or shape.

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All cards in a box are blue. A blue card is on the table. Must it have come from that box?

  1. Yes, certainly
  2. Only if it is square
  3. Only at night
  4. No, not necessarily
Answer and explanation

Correct answer: No, not necessarily

Other blue cards could exist outside the box. The rule gives no exclusive origin for blue cards.

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Mira finished before Arben. Arben finished before Eleni. Who finished first among these three?

  1. Arben
  2. Mira
  3. Eleni
  4. They tied
Answer and explanation

Correct answer: Mira

The stated order is Mira → Arben → Eleni. No speed calculation is needed.

Original example, with the solution above.

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One of three closed boxes holds a key. Box A is empty. What do we know?

  1. The key is in B
  2. The key is in C
  3. The key is in B or C
  4. No box holds a key
Answer and explanation

Correct answer: The key is in B or C

Ruling out A leaves two possibilities. There is no information that chooses between B and C.

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Start at 5. Double it, then add 3. What is the result?

  1. 13
  2. 16
  3. 10
  4. 8
Answer and explanation

Correct answer: 13

Follow the order: 5 × 2 = 10, then 10 + 3 = 13. Adding first would produce 16.

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Some books on a shelf are red. Must every book on that shelf be red?

  1. Yes
  2. Only the large books
  3. Only the first book
  4. No
Answer and explanation

Correct answer: No

“Some” establishes at least one red book. It does not establish that every book is red, nor that some must be another colour.

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Prepared with AI assistance and checks against linked sources. Not all translations have received native-speaker review.

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