# How do you find the LCD between 20c, 12c^2?

Jul 6, 2016

LCD is $60 {c}^{2}$

#### Explanation:

The LCD must be divisible by both $20 c \mathmr{and} 12 {c}^{2}$

One way to find the LCD (especially of only 2 numbers) is to consider the multiples of the larger of the two (20). Look for the first of the multiples which is divisible by the smaller number (12).

20, 40, 60, 80 ...... We should know that 60 is also a multiple of 12.

60 is therefore the LCD of 20 and 12.

$c$ is a factor of ${c}^{2}$ so we can use ${c}^{2}$

LCD is $60 {c}^{2}$

This can also be done by writing each term as the product of its prime factors. However this method is longer and is better for 3 or 4 numbers.

$20 c \text{ " = 2 xx 2xx " } 5 \times c$
$12 {c}^{2} \text{ " = 2xx2xx3 xx " } c \times c$

LCD =$\text{ } 2 \times 2 \times 3 \times 5 \times c \times c = 60 {c}^{2}$