CSS 2025General Science & AbilityQ. 8
(a) A train in first five successive minutes from its start runs 68 m, 127 m, 208 m, 312 m and 535 m and for next 5 minutes maintains an average speed of 33 km/hr. Find the whole distance covered and the average speed in covering this total distance. (b) A solid cuboid with base 10 cm by 6 cm is available. The height of the cuboid is 'y' centimeter and the total surface area of the cuboid is given to be 376 cm². Find the height of the cuboid. (c) In a six member family (A, B, C, D, E and F), there are two fathers, three brothers and a mother. If C is the sister of F, B is the brother of E's husband. D is the father of A and grandfather of F. Who is E's husband? (d) How many prime numbers are between each of the following pairs of numbers? a) √3 and √120 b) √10 and √410 c) ∛10 and ∛999 d) ∛28 and √120 e) √8 and √400.
#cssnexusBy CSS Nexus Team ·
This answer to the CSS 2025 General Science & Ability paper (Q. 8) was written by the CSS Nexus team. Read the outline first, then see how each point is developed.
Outline
- (a) 1,250 m + 2,750 m = 4 km in 10 minutes: 24 km/h
- (b) 2(60 + 16y) = 376: y = 8 cm
- (c) A is E's husband
- (d) Prime counts: 4, 6, 3, 2, 7
Answer
(a) Train
Distance in the first 5 minutes = 68 + 127 + 208 + 312 + 535 = 1,250 m.
Distance in the next 5 minutes = 33 km/h × (5/60) h = 2.75 km = 2,750 m.
Whole distance = 1,250 + 2,750 = 4,000 m = 4 km.
Average speed = total distance ÷ total time = 4 km ÷ (10/60) h = 24 km/h.
(b) Height of the cuboid
Total surface area = 2(lb + bh + lh) = 2(10 × 6 + 6y + 10y) = 2(60 + 16y).
So 2(60 + 16y) = 376, which gives 60 + 16y = 188, 16y = 128, and y = 8 cm.
(c) Family puzzle
D is the father of A and the grandfather of F, so A must be a parent of F. The family has only one mother and two fathers, so D and A are the two fathers, and A is F's father.
C is F's sister, so C is also A's child. B is the brother of E's husband. Since E is married and is the family's only mother, E is the mother of C and F.
This makes E the wife of A, the father of her children. B is A's brother, also a son of D. The three brothers are therefore A, B and F.
A is E's husband.
(d) Prime numbers between the pairs
(a) √3 ≈ 1.73 and √120 ≈ 10.95. The primes are 2, 3, 5 and 7: 4 primes.
(b) √10 ≈ 3.16 and √410 ≈ 20.25. The primes are 5, 7, 11, 13, 17 and 19: 6 primes.
(c) ∛10 ≈ 2.15 and ∛999 ≈ 9.997. The primes are 3, 5 and 7: 3 primes.
(d) ∛28 ≈ 3.04 and √120 ≈ 10.95. The primes are 5 and 7: 2 primes.
(e) √8 ≈ 2.83 and √400 = 20. The primes are 3, 5, 7, 11, 13, 17 and 19: 7 primes.
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