LCM of two integers is 60 and one of the integers is 12. Write down 2 possible values of the other integer.

1 answer

To find the possible values of the other integer \( b \) given that the least common multiple (LCM) of \( 12 \) and \( b \) is \( 60 \), we can use the relationship:

\[ \text{LCM}(a, b) = \frac{|a \cdot b|}{\text{GCD}(a, b)} \]

Where:

  • \( a = 12 \)
  • \( \text{LCM} = 60 \)

We can rearrange the formula to find \( b \):

\[ b = \frac{\text{LCM}(a, b) \cdot \text{GCD}(a, b)}{a} \]

Now, we need to find possible values for \( b \) such that this relationship holds.

First, we can find the GCD of \( 12 \) and \( b \):

  • The factors of \( 12 \) are \( 1, 2, 3, 4, 6, 12 \).
  • The GCD must be one of these factors.

We'll calculate possible values for \( b \) using the values of the GCD.

  1. If GCD(12, b) = 12: \[ LCM(12, b) = \frac{12 \cdot b}{12} = b \] Setting \( b = 60 \) does not work since that's not equal to 12.

  2. If GCD(12, b) = 6: \[ 60 = \frac{12 \cdot b}{6} \implies 60 = 2b \implies b = 30 \]

  3. If GCD(12, b) = 4: \[ 60 = \frac{12 \cdot b}{4} \implies 60 = 3b \implies b = 20 \]

  4. If GCD(12, b) = 3: \[ 60 = \frac{12 \cdot b}{3} \implies 60 = 4b \implies b = 15 \]

  5. If GCD(12, b) = 2: \[ 60 = \frac{12 \cdot b}{2} \implies 60 = 6b \implies b = 10 \]

  6. If GCD(12, b) = 1: \[ 60 = \frac{12 \cdot b}{1} \implies 60 = 12b \implies b = 5 \]

Thus, the possible values for \( b \) are \( 30, 20, 15, 10, \) and \( 5 \).

Two possible values of the other integer \( b \) are:

  • \( 30 \)
  • \( 20 \)

These will satisfy that \( \text{LCM}(12, b) = 60 \).