Find the lowest common multiple (LCM) of 56 and 42
The Correct Answer and Explanation is:
Answer:
The lowest common multiple (LCM) of 56 and 42 is 168.
Explanation:
To find the lowest common multiple (LCM) of two numbers, we are looking for the smallest number that is divisible by both original numbers. This is useful in solving problems involving synchronization, scheduling, or combining different repeating cycles.
There are multiple ways to find the LCM, but one of the most efficient is by using the prime factorization method or the formula involving the greatest common divisor (GCD).
Step 1: Prime Factorization
- 56 = 2 × 2 × 2 × 7 = 2³ × 7
- 42 = 2 × 3 × 7 = 2 × 3 × 7
To find the LCM, take the highest powers of all the prime factors that appear in either number:
- 2³ (from 56)
- 3¹ (from 42)
- 7¹ (common to both)
Now multiply the highest powers:
- LCM = 2³ × 3 × 7 = 8 × 3 × 7 = 24 × 7 = 168
Step 2: Using the GCD
You can also use this formula: LCM(a,b)=a×bGCD(a,b)\text{LCM}(a, b) = \frac{a \times b}{\text{GCD}(a, b)}LCM(a,b)=GCD(a,b)a×b
- Find the GCD of 56 and 42.
The common factors are:- 56 = 2³ × 7
- 42 = 2 × 3 × 7
⇒ GCD = 2 × 7 = 14
- Now apply the formula: LCM(56,42)=56×4214=235214=168\text{LCM}(56, 42) = \frac{56 × 42}{14} = \frac{2352}{14} = 168LCM(56,42)=1456×42=142352=168
Conclusion:
The LCM of 56 and 42 is 168, meaning 168 is the smallest number that both 56 and 42 divide evenly into. This result is confirmed using both prime factorization and the GCD method, making the answer reliable and mathematically sound.
