Logical Deduction — PPSC previous year questions

Rahul's range 'after 15th but before 18th' allows the 16th or 17th; Priyanka's 'after 16th but before 19th' allows the 17th or 18th. The only date in both ranges is the 17th.

There are 8 balls and the odd one may be heavier or lighter. So there are 8 × 2 = 16 possibilities. Each weighing has three outcomes: left down, right down, or balance. Two weighings separate at most 3² = 9 cases, which is too few. Three weighings separate up to 3³ = 27, which is at least 16. A working plan also exists: weigh 3 against 3, then split according to the result. > 3² = 9 < 16 → 2 weighings insufficient > 3³ = 27 ≥ 16 → 3 weighings suffice So the least number of weighings is 3.

“Rain at night ⇒ cloudy morning” guarantees nothing in the reverse direction: a cloudy morning can arise from other causes, so last night's rain is possible but not certain. Concluding (a) from a cloudy morning is the fallacy of affirming the consequent, and the statement says nothing at all about tonight, which rules out (c) and (d).

Each full day-and-night the snail gains 5 − 4 = 1 m. After 15 such days it stands at 15 m; on the 16th day it climbs 5 m and reaches the 20 m rim, so it never slides back. > 15 days × 1 m = 15 m > Day 16: 15 + 5 = 20 m → out So 16 days. The trap answer of 20 days ignores that the snail escapes during the final climb.

Each word goes with the number naturally linked to it. A triangle has 3 sides. A glove has 5 fingers. A clock face shows 12 hours. A bicycle has 2 wheels.

A good hypothesis must be an empirical claim. You must be able to check it against observation. It must also be able to turn out false. 'Intelligent persons have good memory' links two measurable variables. It can be tested on a sample. It is refuted if intelligent people are found with poor memory. 'Some birds are animals' is true by definition. 'Some businessmen are dishonest' is a vague existential claim. One example confirms it and nothing can refute it. 'All men are mortal' is a universally accepted truth, not a testable research hypothesis.

Subtract to see which is bigger: P − Q = 0.15B − 0.10A, and its sign depends on how much A beats B. > A = 1.1, B = 1 → P − Q = +0.04, so P > Q > A = 2, B = 1 → P − Q = −0.05, so Q > P Both outcomes are possible, so nothing can be concluded with certainty.

Let the total prizes be T. 'All seed pens but 6' means the seed pens number T − 6. The same holds for flower pots and soy candles. > (T − 6) + (T − 6) + (T − 6) = T > 3T − 18 = T → 2T = 18 → T = 9 So there are 9 prizes, three of each kind.

Through the lens every colour shifts one step along the spectrum towards red: violet → indigo, blue → green, green → yellow, so yellow → orange and orange → red. Galileo sees red, so the fruit is actually orange in colour, i.e. an orange. An apple (red) would appear as whatever lies beyond red, a banana (yellow) would look orange and a guava (green) would look yellow.

The conclusion 'All humans are mortal' comes from a few observed cases. A, B, C and D are each human and mortal. Moving from cases to a general rule is the mark of an inductive argument. The premises make the conclusion probable, but do not prove it. A deductive argument, including a syllogism, works the other way. It moves from general premises to a conclusion that must follow.