GyaanVibe is a focused educational platform dedicated to helping SSC CGL aspirants crack Tier 1 & Tier 2 exam with a strategic, day-wise, and well-structured preparation approach.
SSC CGL Preparation – Day 1
✅ Practice MCQs – Number System
1. What is the HCF of 60 and 72?
A) 6
B) 12
C) 18
D) 24
Answer: B) 12
Solution:
60 = 2² × 3 × 5
72 = 2³ × 3²
HCF = 2² × 3 = 4 × 3 = 12
2. What is the least number which when divided by 12, 15, and 20 leaves a remainder 3 in each case?
A) 63
B) 123
C) 243
D) 303
Answer: D) 303
Solution:
LCM of 12, 15, 20 = 60
Required number = 60k + 3
Try smallest: 60 × 5 = 300 → 300 + 3 = 303
3. The number of zeros at the end of 80! is:
A) 16
B) 18
C) 19
D) 20
Answer: C) 19
Solution:
No. of 5s in 80! = ⌊80/5⌋ + ⌊80/25⌋ + ⌊80/125⌋
= 16 + 3 + 0 = 19
4. What is the LCM of 18, 24, and 30?
A) 180
B) 120
C) 360
D) 240
Answer: A) 360
Solution:
18 = 2 × 3²
24 = 2³ × 3
30 = 2 × 3 × 5
LCM = 2³ × 3² × 5 = 360
5. Which of the following numbers is divisible by 11?
A) 2145
B) 1342
C) 1234
D) 1430
Answer: A) 2145
Solution:
Alternating sum = 2 – 1 + 4 – 5 = 0 → divisible by 11 → 2145
6. How many divisors does 360 have?
A) 24
B) 28
C) 32
D) 36
Answer: A) 24
Solution:
360 = 2³ × 3² × 5
Divisors = (3+1)(2+1)(1+1) = 4×3×2 = 24
7. If the sum of two numbers is 48 and their HCF is 6, which of the following could be the pair?
A) 18 and 30
B) 24 and 36
C) 12 and 36
D) 6 and 42
Answer: A) 18 and 30
Solution:
HCF of 18 and 30 = 6, and 18 + 30 = 48 → ✅
8. Which one is an irrational number?
A) √4
B) √16
C) √5
D) 0.25
Answer: C) √5
Solution:
√5 is irrational, not a perfect square.
9. If HCF of two numbers is 14 and their product is 1960, then their LCM is:
A) 140
B) 196
C) 240
D) 280
Answer: D) 280
Solution:
Product = HCF × LCM ⇒
LCM = 1960 / 14 = 140
10. Find the smallest 4-digit number divisible by 6, 8, and 12.
A) 1008
B) 1024
C) 1032
D) 1040
Answer: A) 1008
Solution:
LCM of 6, 8, 12 = 24
Smallest 4-digit number = 1000
Next multiple of 24 after 1000 = 1008
