Logical Reasoning and Puzzles Flashcards

A sequence follows the rule that each term equals the sum of the two preceding terms. If the 5th term is 12 and the 6th term is 20, what is the 4th term?

Answer: 8

Since 6th = 5th + 4th, we get 20 = 12 + 4th term, so 4th term = 8.

All metals conduct electricity. Iron is a metal. Zinc is a metal. Carbon does not conduct electricity. Which fact contradicts the given premise?

Answer: Carbon does not conduct electricity

If all metals conduct electricity but carbon does not, and carbon is sometimes classified as a semi-metal, this conflicts with the universal statement.

Three switches in one room control three bulbs in another. You may flip switches freely, then visit the other room once. How do you identify all three bulbs?

Answer: Turn on switch 1 for a while, turn it off, then turn on switch 2, then enter

The warm-off bulb maps to switch 1, the lit bulb maps to switch 2, and the cold-off bulb maps to switch 3.

In a group of 50 students, 30 play cricket, 25 play football, and 10 play both. How many play neither sport?

Answer: 5

By inclusion-exclusion: 30 + 25 − 10 = 45 play at least one sport; 50 − 45 = 5 play neither.

A train 200 m long passes a stationary pole in 10 seconds. How long will it take to pass a 300 m platform?

Answer: 25 s

Speed = 200/10 = 20 m/s; total distance = 200 + 300 = 500 m; time = 500/20 = 25 s.

If PENCIL is coded with each letter shifted +3 positions in the alphabet, what is the code?

Answer: SHQFLO

P+3=S, E+3=H, N+3=Q, C+3=F, I+3=L, L+3=O → SHQFLO.

A mirror is placed vertically along the right side of the word 'BED'. What is the mirror image?

Answer: The word reverses and each letter flips

A vertical mirror placed to the right reverses the order of letters and flips each letter horizontally.