Subtracting Fractions with Unlike Denominators

This video tutorial explains how to subtract fractions with unlike denominators. It emphasizes the importance of finding a common denominator, either by multiplying the denominators or using the least common multiple. The tutorial demonstrates using prime factorization to find the least common denominator and shows how to subtract the numerators once a common denominator is established. Finally, it covers simplifying the resulting fraction by identifying common factors.

Why is it necessary to have a common denominator when subtracting fractions?

• To simplify the fractions

• To make the numerators equal

• To convert fractions to decimals

• To ensure the fractions are of the same size

What is the least common denominator?

• The sum of the denominators

• The difference between the denominators

• The smallest number divisible by both denominators

• The largest number divisible by both denominators

How can you find the least common denominator using prime factorization?

• By finding the common prime factors and multiplying them

• By multiplying the prime factors of both denominators

• By dividing the prime factors of both denominators

• By adding the prime factors of both denominators

What is the next step after finding a common denominator?

• Add the numerators

• Subtract the numerators

• Multiply the numerators

• Divide the numerators

What is the result of subtracting 2/21 from 4/15 after finding a common denominator?

• 6/35

• 10/105

• 28/105

• 18/105

What common factor do 18 and 105 share?

• 2

• 7

• 3

• 5

How can you simplify the fraction 18/105?

• By dividing both numerator and denominator by 3

• By dividing both numerator and denominator by 2

• By dividing both numerator and denominator by 7

• By dividing both numerator and denominator by 5

What is the simplified form of the fraction 18/105?

• 12/35

• 3/35

• 6/35

• 9/52

Which method can be used to show the simplification of a fraction?

• Adding the numerator and denominator

• Multiplying both by their least common multiple

• Subtracting the numerator from the denominator

• Dividing both by their greatest common factor

What is the final simplified difference of the fractions 4/15 and 2/21?

• 10/105

• 28/105

• 18/105

• 6/35