Pre-Algebra Demystified

 Step 1 Arrange the numbers in the denominators in a row.

 Step 2 Divide by the smallest number that divides evenly into two or

more of the numbers.

 Step 3 Bring down to the next row all quotients and remaining numbers

not used.

 Step 4 Continue dividing until no two of the denominators can be

divided evenly by any number other than one.

 Step 5 Multiply all the divisors and the remaining numbers to get the

lowest common denominator.

EXAMPLE
Find the lowest common denominator of the fractions 165 ,^38 , and 241.

SOLUTION
Arrange the numbers in a row and start dividing, as shown:

2 Þ 16 8 24

2 Þ 8412

2 Þ 42 6

21 3

After dividing by 2 three times, there are no two numbers in the last row that
can be divided by any number other than one, so you stop. Multiply the
divisors and the numbers in the bottom row to get the lowest common
denominator. 2 2  2  2  1  3 ¼48. Hence, the lowest common
denominator of the fractions 165 ,^38 , and 241 is 48.

EXAMPLE
Find the lowest common denominator of 203 , 152 , and 307.

SOLUTION

2 Þ 20 15 30

3 Þ 10 15 15

5 Þ 10 5 5

211

Hence, the LCD is 2 3  5  2  1  1 ¼60.

CHAPTER 4 Fractions: Part 2 55