Solving LCM Problems

 

Nigerian Navy Secondary Schools Entrance Examination

Mathematics & Quantitative Reasoning Past Questions Guide

What is LCM?

LCM (Lowest Common Multiple) is the smallest positive integer that is perfectly divisible by a given set of numbers without leaving any remainder.

Example: The LCM of 4 and 6 is 12 because 12 is the smallest number that both 4 and 6 can divide into evenly.

Practice Questions & Solutions

1. Find the Lowest Common Multiple (L.C.M) of 12, 18, and 24.

• A) 36
• B) 48
• C) 72
• D) 144

Solution:
Prime factors: 12 = 2² × 3, 18 = 2 × 3², 24 = 2³ × 3.
LCM = 2³ × 3² = 8 × 9 = 72.
Correct Answer: C) 72

2. Simplify: (0.2 × 0.01) / 0.0002

• A) 1
• B) 10
• C) 100
• D) 2

Solution:
0.2 × 0.01 = 0.002.
0.002 / 0.0002 = 20 / 2 = 10.
Correct Answer: B) 10

3. What is the difference between 100 and 99.991?

• A) 0.009
• B) 0.01
• C) 0.09
• D) 0.001

Solution:
100.000 - 99.991 = 0.009.
Correct Answer: A) 0.009

4. A line that divides a circle into two equal halves is called a _______.

• A) Chord
• B) Radius
• C) Segment
• D) Diameter

Solution:
The diameter passes through the center of a circle and divides it into two equal semicircles.
Correct Answer: D) Diameter

5. Change 1 hour 5 minutes 10 seconds to seconds.

• A) 3600 seconds
• B) 3910 seconds
• C) 3900 seconds
• D) 4110 seconds

Solution:
1 hr = 3600s; 5 mins = 300s; Total = 3600 + 300 + 10 = 3910 seconds.
Correct Answer: B) 3910 seconds

6. What is the place value of 7 in 45.372?

• A) Tens
• B) Tenths
• C) Hundredths
• D) Thousandths

Solution:
The first digit after the decimal point is tenths (3), the second digit is hundredths (7).
Correct Answer: C) Hundredths

7. A car uses 1 litre of petrol for every 14km. If 1 litre costs ₦250.00, how far can the car go with ₦1,500.00 worth of petrol?

• A) 70km
• B) 84km
• C) 98km
• D) 112km

Solution:
Litres bought = 1500 / 250 = 6 litres.
Distance = 6 × 14 = 84km.
Correct Answer: B) 84km

8. Correct 0.002473 to 3 significant figures.

• A) 0.002
• B) 0.00247
• C) 0.00248
• D) 0.0025

Solution:
Count significant figures starting from the first non-zero digit (2, 4, 7). The next digit is 3, so round down.
Correct Answer: B) 0.00247

9. Quantitative Reasoning: If 4 Δ 2 = 10 and 5 Δ 3 = 13, find 7 Δ 4.

• A) 11
• B) 18
• C) 19
• D) 22

Solution:
The logic pattern is: (First number × 2) + Second number.
For 7 Δ 4: (7 × 2) + 4 = 14 + 4 = 18.
Correct Answer: B) 18

10. An angle on a straight line is equal to ______ degrees.

• A) 90°
• B) 180°
• C) 270°
• D) 360°

Solution:
Angles on a straight line always sum up to exactly 180 degrees.
Correct Answer: B) 180°