Answer:
3/100 (Decimal Form: 0.03)
Explanation:
Find the Least Common Denominator (LCD) of 21/25 , 81/100. In other words, find the Least Common Multiple (LCM) of 25,100.
Method 1: By Listing Multiples
- List the multiples of each number.
Multiples of 25 : 25, 50, 75, 100, ...
Multiples of 100 : 100, ...
- Find the smallest number that is shared by all rows above. This is the LCM.
LCM is 100.
Method 2: By Prime Factors
- List the prime factors of each number.
Prime Factors of 25 : 5, 5
Prime Factors of 100 : 2, 2, 5, 5
- Find the union of these primes.
2, 2, 5, 5
- Multiply these numbers: 2 * 2 * 5 * 5 = 100. This is the LCM.
LCM = 100
Make the denominators the same as the LCD.
21 * 4/25 * 4 - 81/100
Simplify. Denominators are now the same.
84/100 - 81/100
Join the denominators.
84-81/100
Simplify.
3/100 (Decimal Form: 0.03)