SSC CGL Quant – Statistics & Probability – Level 3 · Challenge
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Mean 10; squared deviations 16 + 4 + 0 + 4 + 16 = 40; 40/5 = 8.
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SSC CGL Quant – Statistics & Probability – Level 3 · Challenge – 8 questions, subject: Quantitative Aptitude. Every question has the correct answer with a one-line explanation; tap "Show Answer". Free practice for TNPSC, UPSC, SSC, Bank and RRB exams – Shanmugam IAS Academy, Coimbatore.
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1.
For the travel-time data (classes 0–10, 10–20, 20–30, 30–40, 40–50 with frequencies 3, 10, 14, 8, 5), the median is:
Correct Answer: C [25 minutes]
Explanation:
N/2 = 20; cf before 20–30 is 13 → 20 + (20 − 13)/14 × 10 = 25.
2.
For the same data, the mode is:
Correct Answer: B [24 minutes]
Explanation:
l + (f₁ − f₀)/(2f₁ − f₀ − f₂) × h = 20 + 4/10 × 10 = 24.
3.
Assertion–Reason
A: If every observation is increased by 10, the standard deviation does not change.
R: Adding a constant shifts every value and the mean by the same amount, so the deviations stay the same.
A: If every observation is increased by 10, the standard deviation does not change.
R: Adding a constant shifts every value and the mean by the same amount, so the deviations stay the same.
Correct Answer: A [Both A and R are true and R explains A]
Explanation:
x − x̄ is unchanged when both move by 10, so SD is unchanged.
4.
A bag has 5 red, 4 blue and 3 green balls. One ball is drawn at random. The probability that it is NOT blue is:
Correct Answer: C [2/3]
Explanation:
Not blue = 8 of 12 = 2/3.
5.
A number is chosen at random from 1 to 30. The probability that it is a multiple of 3 or 5 is:
Correct Answer: B [7/15]
Explanation:
Multiples of 3: 10, of 5: 6, of 15: 2 → 10 + 6 − 2 = 14 → 14/30 = 7/15.
6.
The mean of 25 numbers is 36. The mean of the first 13 is 32 and the mean of the last 13 is 39. The 13th number is:
Correct Answer: D [23]
Explanation:
32 × 13 + 39 × 13 − 25 × 36 = 416 + 507 − 900 = 23 (the 13th number is counted twice).
7.
True/False countHow many of these statements are true?
I. The mean of 1, 2, …, n is (n + 1)/2.
II. A probability can be 1.2.
III. With two dice, the sum 7 is the most likely sum.
I. The mean of 1, 2, …, n is (n + 1)/2.
II. A probability can be 1.2.
III. With two dice, the sum 7 is the most likely sum.
Correct Answer: C [Only 2]
Explanation:
I true, III true (6 ways); II false – a probability never exceeds 1.
8.
The variance of 6, 8, 10, 12, 14 is:
Correct Answer: A [8]
Explanation:
Mean 10; squared deviations 16 + 4 + 0 + 4 + 16 = 40; 40/5 = 8.
➤ Full notes, shortcuts and every answer explained – SSC CGL 2026 Quantitative Aptitude book (₹149): www.shanmugamiasacademy.in/study-materials/ssc-cgl-quantitative-aptitude
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