Least common denominator - Examples, Exercises and Solutions

A common denominator is a denominator that will be common and equal for all the fractions in the exercise. We will reach such a denominator by reducing or enlarging the fraction - an operation of multiplication or division.
We can arrive at several correct common denominators.

We will divide the search for the common denominator into 3 cases:

  • The first case: one of the denominators appearing in the original exercise will be the common denominator.
    In this case, we will notice that we only have to multiply one denominator by an integer to reach the same denominator as in the other fraction.
  • The second case: find a number that both denominators in the exercise can reach by multiplication.
  • The third case: find the common denominator by multiplying the denominators.

Suggested Topics to Practice in Advance

  1. A fraction as a divisor
  2. Numerator
  3. Denominator
  4. Fractions
  5. Part of a quantity
  6. Placing Fractions on the Number Line

Practice Least common denominator

examples with solutions for least common denominator

Exercise #1

48+410= \frac{4}{8}+\frac{4}{10}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common multiple between 8 and 10

To find the lowest common multiple, we need to find a number that is divisible by both 8 and 10

In this case, the lowest common multiple is 40

Now, let's multiply each number in the appropriate multiples to reach the number 40

We will multiply the first number by 5

We will multiply the second number by 4

4×58×5+4×410×4=2040+1640 \frac{4\times5}{8\times5}+\frac{4\times4}{10\times4}=\frac{20}{40}+\frac{16}{40}

Now let's calculate:

20+1640=3640 \frac{20+16}{40}=\frac{36}{40}

Answer

3640 \frac{36}{40}

Exercise #2

51016= \frac{5}{10}-\frac{1}{6}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common multiple between 6 and 10

To find the lowest common multiple, we need to find a number that is divisible by both 6 and 10

In this case, the lowest common multiple is 30

Now let's multiply each number by an appropriate factor to reach the multiple of 30

We will multiply the first number by 3

We will multiply the second number by 5

5×310×31×56×5=1530530 \frac{5\times3}{10\times3}-\frac{1\times5}{6\times5}=\frac{15}{30}-\frac{5}{30}

Now let's subtract:

15530=1030 \frac{15-5}{30}=\frac{10}{30}

Answer

1030 \frac{10}{30}

Exercise #3

2316612= \frac{2}{3}-\frac{1}{6}-\frac{6}{12}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common multiple of 3, 6 and 12

To find the lowest common multiple, we find a number that is divisible by 3, 6 and 12

In this case, the common multiple is 12

Now let's multiply each number in the appropriate multiple to reach the multiple of 12

We will multiply the first number by 4

We will multiply the second number by 2

We will multiply the third number by 1

2×43×41×26×26×112×1=812212612 \frac{2\times4}{3\times4}-\frac{1\times2}{6\times2}-\frac{6\times1}{12\times1}=\frac{8}{12}-\frac{2}{12}-\frac{6}{12}

Now let's subtract:

82612=6612=012 \frac{8-2-6}{12}=\frac{6-6}{12}=\frac{0}{12}

We will divide the numerator and the denominator by 0 and get:

012=0 \frac{0}{12}=0

Answer

0 0

Exercise #4

12+38= \frac{1}{2}+\frac{3}{8}=

Video Solution

Answer

78 \frac{7}{8}

Exercise #5

24+12= \frac{2}{4}+\frac{1}{2}=

Video Solution

Answer

1 1

examples with solutions for least common denominator

Exercise #1

23+16= \frac{2}{3}+\frac{1}{6}=

Video Solution

Answer

56 \frac{5}{6}

Exercise #2

24+18= \frac{2}{4}+\frac{1}{8}=

Video Solution

Answer

58 \frac{5}{8}

Exercise #3

15+610= \frac{1}{5}+\frac{6}{10}=

Video Solution

Answer

810 \frac{8}{10}

Exercise #4

13+36= \frac{1}{3}+\frac{3}{6}=

Video Solution

Answer

56 \frac{5}{6}

Exercise #5

34+18= \frac{3}{4}+\frac{1}{8}=

Video Solution

Answer

78 \frac{7}{8}

examples with solutions for least common denominator

Exercise #1

14+612= \frac{1}{4}+\frac{6}{12}=

Video Solution

Answer

912 \frac{9}{12}

Exercise #2

26+412= \frac{2}{6}+\frac{4}{12}=

Video Solution

Answer

812 \frac{8}{12}

Exercise #3

13+29= \frac{1}{3}+\frac{2}{9}=

Video Solution

Answer

59 \frac{5}{9}

Exercise #4

14+58= \frac{1}{4}+\frac{5}{8}=

Video Solution

Answer

78 \frac{7}{8}

Exercise #5

13+49= \frac{1}{3}+\frac{4}{9}=

Video Solution

Answer

79 \frac{7}{9}

Topics learned in later sections

  1. How do you simplify fractions?
  2. Simplification and Expansion of Simple Fractions