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BECE Mathematics 2018 Paper

Question : 8

Total: 40

Solution:

List the multiples of each and select the least number which appears in all

Multiples of

10=10, 10+10=20, 20+10=30, 30+10=40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, \ldots

Multiples of

15=15, 15+15=30, 30+15=45, 45+15=60, 75, 90, 105, 120, 135, 150, 165, \ldots

Multiples of

25=25, 25+25=50, 50+25=75, 75+25=100, 125, 150, 175, 200 \ldots

Alternatively

HOW TO: FIND THE L.C.M USING THE PRIME FACTORS METHOD

Step 1. Find the prime factorization of each number.

Step 2. Write each number as a product of primes.

Step 3. The L.C.M is the product (multiplication) of each of the prime numbers in its highest power.

Step 1 & 2

\;10 = 2 \times 5

\;15 = 3 \times 5

25 = 5 \times 5 = 5^2

Step 3

\; \text{L.C.M} \; = 2 \times 3 \times 5^2 = 6 \times 25 = 150

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