Examples with solutions for Common Denominators: One of the denominators is the common denominator

Exercise #1

What is the least common multiple of these two numbers?

10   15 \boxed{10}~~~\boxed{15}

Step-by-Step Solution

To find the least common multiple (LCM) of 10 10 and 15 15 , we list the multiples of each number:

  • Multiples of 10 10 are 10,20,30,40, 10, 20, 30, 40, \ldots
  • Multiples of 15 15 are 15,30,45, 15, 30, 45, \ldots

The smallest common multiple is 30 30 .

Answer

30

Exercise #2

What is the least common multiple of these two numbers?

3   9 \boxed{3}~~~\boxed{9}

Step-by-Step Solution

To find the least common multiple (LCM) of 3 3 and 9 9 , we list the multiples of each number:

  • Multiples of 3 3 are 3,6,9,12,15, 3, 6, 9, 12, 15, \ldots
  • Multiples of 9 9 are 9,18,27, 9, 18, 27, \ldots

The smallest common multiple is 9 9 .

Answer

9

Exercise #3

What is the least common multiple of these two numbers?

4   8 \boxed{4}~~~\boxed{8}

Step-by-Step Solution

To find the least common multiple (LCM) of 4 4 and 8 8 , we list the multiples of each number:

  • Multiples of 4 4 are 4,8,12,16,20, 4, 8, 12, 16, 20, \ldots
  • Multiples of 8 8 are 8,16,24, 8, 16, 24, \ldots

The smallest common multiple is 8 8 .

Answer

8

Exercise #4

What is the least common multiple of these two numbers?

5   10 \boxed{5}~~~\boxed{10}

Step-by-Step Solution

To find the least common multiple (LCM) of 5 5 and 10 10 , we list the multiples of each number:

  • Multiples of 5 5 are 5,10,15,20, 5, 10, 15, 20, \ldots
  • Multiples of 10 10 are 10,20,30, 10, 20, 30, \ldots

The smallest common multiple is 10 10 .

Answer

10

Exercise #5

What is the least common multiple of these two numbers?

6   9 \boxed{6}~~~\boxed{9}

Step-by-Step Solution

To find the least common multiple (LCM) of 6 6 and 9 9 , we list the multiples of each number:

  • Multiples of 6 6 are 6,12,18,24, 6, 12, 18, 24, \ldots
  • Multiples of 9 9 are 9,18,27, 9, 18, 27, \ldots

The smallest common multiple is 18 18 .

Answer

18

Exercise #6

What is the least common multiple of these two numbers?

7   14 \boxed{7}~~~\boxed{14}

Step-by-Step Solution

To find the least common multiple (LCM) of 7 7 and 14 14 , we list the multiples of each number:

  • Multiples of 7 7 are 7,14,21,28, 7, 14, 21, 28, \ldots
  • Multiples of 14 14 are 14,28,42, 14, 28, 42, \ldots

The smallest common multiple is 14 14 .

Answer

14

Exercise #7

What is the least common multiple of these two numbers?

8   12 \boxed{8}~~~\boxed{12}

Step-by-Step Solution

To find the least common multiple (LCM) of 8 8 and 12 12 , we list the multiples of each number:

  • Multiples of 8 8 are 8,16,24,32, 8, 16, 24, 32, \ldots
  • Multiples of 12 12 are 12,24,36, 12, 24, 36, \ldots

The smallest common multiple is 24 24 .

Answer

24

Exercise #8

What is the least common multiple of:

5   10   20 \boxed{5}~~~\boxed{10} ~~~\boxed{20}

Step-by-Step Solution

To find the least common multiple (LCM) of 5 5 , 10 10 , and 20 20 , find their prime factorizations:

5=5 5 = 5

10=2×5 10 = 2 \, \times \, 5

20=22×5 20 = 2^2 \, \times \, 5

× \times The LCM is determined by selecting the greatest power of each prime number:

22 2^2 from 20 and 5 5 .

The LCM is 22×5=4×5=20 2^2 \, \times \, 5 = 4 \, \times \, 5 = 20 .

Answer

20

Exercise #9

Solve the following exercise:

12+210= \frac{1}{2}+\frac{2}{10}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common denominator between 2 and 10

To find the lowest common denominator, we need to find a number that is divisible by both 2 and 10

In this case, the common denominator is 10

Now we'll multiply each fraction by the appropriate number to reach the denominator 10

We'll multiply the first fraction by 5

We'll multiply the second fraction by 1

1×52×5+2×110×1=510+210 \frac{1\times5}{2\times5}+\frac{2\times1}{10\times1}=\frac{5}{10}+\frac{2}{10}

Now we'll combine and get:

5+210=710 \frac{5+2}{10}=\frac{7}{10}

Answer

710 \frac{7}{10}

Exercise #10

Solve the following exercise:

12+310= \frac{1}{2}+\frac{3}{10}=

Video Solution

Step-by-Step Solution

Let's try to find the least common denominator between 2 and 10

To find the least common denominator, we need to find a number that is divisible by both 2 and 10

In this case, the common denominator is 10

Now we'll multiply each fraction by the appropriate number to reach the denominator 10

We'll multiply the first fraction by 5

We'll multiply the second fraction by 1

1×52×5+3×110×1=510+310 \frac{1\times5}{2\times5}+\frac{3\times1}{10\times1}=\frac{5}{10}+\frac{3}{10}

Now we'll combine and get:

5+310=810 \frac{5+3}{10}=\frac{8}{10}

Answer

810 \frac{8}{10}

Exercise #11

Solve the following exercise:

13+59= \frac{1}{3}+\frac{5}{9}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common denominator between 3 and 9

To find the lowest common denominator, we need to find a number that is divisible by both 3 and 9

In this case, the common denominator is 9

Now we'll multiply each fraction by the appropriate number to reach the denominator 9

We'll multiply the first fraction by 3

We'll multiply the second fraction by 1

1×33×3+5×19×1=39+59 \frac{1\times3}{3\times3}+\frac{5\times1}{9\times1}=\frac{3}{9}+\frac{5}{9}

Now we'll combine and get:

3+59=89 \frac{3+5}{9}=\frac{8}{9}

Answer

89 \frac{8}{9}

Exercise #12

Solve the following exercise:

14+48= \frac{1}{4}+\frac{4}{8}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common denominator between 4 and 8

To find the lowest common denominator, we need to find a number that is divisible by both 4 and 8

In this case, the common denominator is 8

Now we'll multiply each fraction by the appropriate number to reach the denominator 8

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

1×24×2+4×18×1=28+48 \frac{1\times2}{4\times2}+\frac{4\times1}{8\times1}=\frac{2}{8}+\frac{4}{8}

Now we'll combine and get:

2+48=68 \frac{2+4}{8}=\frac{6}{8}

Answer

68 \frac{6}{8}

Exercise #13

Solve the following exercise:

14+68= \frac{1}{4}+\frac{6}{8}=

Video Solution

Step-by-Step Solution

Let's try to find the least common denominator between 4 and 8

To find the least common denominator, we need to find a number that is divisible by both 4 and 8

In this case, the common denominator is 8

Now we'll multiply each fraction by the appropriate number to reach the denominator 8

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

1×24×2+6×18×1=28+68 \frac{1\times2}{4\times2}+\frac{6\times1}{8\times1}=\frac{2}{8}+\frac{6}{8}

Now we'll combine and get:

2+68=88=1 \frac{2+6}{8}=\frac{8}{8}=1

Answer

1 1

Exercise #14

Solve the following exercise:

15+215= \frac{1}{5}+\frac{2}{15}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common denominator between 5 and 15

To find the lowest common denominator, we need to find a number that is divisible by both 5 and 15

In this case, the common denominator is 15

Now we'll multiply each fraction by the appropriate number to reach the denominator 15

We'll multiply the first fraction by 3

We'll multiply the second fraction by 1

1×35×3+2×115×1=315+215 \frac{1\times3}{5\times3}+\frac{2\times1}{15\times1}=\frac{3}{15}+\frac{2}{15}

Now we'll combine and get:

3+215=515 \frac{3+2}{15}=\frac{5}{15}

Answer

515 \frac{5}{15}

Exercise #15

Solve the following exercise:

35+215= \frac{3}{5}+\frac{2}{15}=

Video Solution

Step-by-Step Solution

Let's try to find the lowest common denominator between 5 and 15

To find the lowest common denominator, we need to find a number that is divisible by both 5 and 15

In this case, the common denominator is 15

Now we'll multiply each fraction by the appropriate number to reach the denominator 15

We'll multiply the first fraction by 3

We'll multiply the second fraction by 1

3×35×3+2×115×1=915+215 \frac{3\times3}{5\times3}+\frac{2\times1}{15\times1}=\frac{9}{15}+\frac{2}{15}

Now we'll combine and get:

9+215=1115 \frac{9+2}{15}=\frac{11}{15}

Answer

1115 \frac{11}{15}

Exercise #16

Solve the following equation:

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

Video Solution

Step-by-Step Solution

Let's first identify the lowest common denominator between 2 and 8.

In order to determine the lowest common denominator, we need to first find a number that is divisible by both 2 and 8.

In this case, the common denominator is 8.

We'll then proceed to multiply each fraction by the appropriate number in order to reach the denominator 8.

We'll multiply the first fraction by 4

We'll multiply the second fraction by 1

1×42×4+3×18×1=48+38 \frac{1\times4}{2\times4}+\frac{3\times1}{8\times1}=\frac{4}{8}+\frac{3}{8}

Finally we'll combine and obtain the following:

4+38=78 \frac{4+3}{8}=\frac{7}{8}

Answer

78 \frac{7}{8}

Exercise #17

Solve the following equation:

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

Video Solution

Step-by-Step Solution

We must first identify the lowest common denominator between 3 and 9.

In order to determine the lowest common denominator, we need to find a number that is divisible by both 3 and 9.

In this case, the common denominator is 9.

We will then proceed to multiply each fraction by the appropriate number to reach the denominator 9.

We'll multiply the first fraction by 3

We'll multiply the second fraction by 1

1×33×3+2×19×1=29+29 \frac{1\times3}{3\times3}+\frac{2\times1}{9\times1}=\frac{2}{9}+\frac{2}{9}

Finally we'll combine and obtain the following:

2+39=59 \frac{2+3}{9}=\frac{5}{9}

Answer

59 \frac{5}{9}

Exercise #18

Solve the following equation:

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

Video Solution

Step-by-Step Solution

We must first identify the lowest common denominator between 3 and 6.

In order to determine the lowest common denominator, we need to find a number that is divisible by both 3 and 6.

In this case, the common denominator is 6.

We'll then proceed to multiply each fraction by the appropriate number to reach the denominator 6.

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

1×23×2+3×16×1=26+36 \frac{1\times2}{3\times2}+\frac{3\times1}{6\times1}=\frac{2}{6}+\frac{3}{6}

Finally we'll combine and obtain the following:

2+36=56 \frac{2+3}{6}=\frac{5}{6}

Answer

56 \frac{5}{6}

Exercise #19

Solve the following equation:

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

Video Solution

Step-by-Step Solution

We must first identify the lowest common denominator between 3 and 9.

In order to determine the lowest common denominator, we need to find a number that is divisible by both 3 and 9.

In this case, the common denominator is 9.

We will then proceed to multiply each fraction by the appropriate number to reach the denominator 9.

We'll multiply the first fraction by 3

We'll multiply the second fraction by 1

1×33×3+4×19×1=39+49 \frac{1\times3}{3\times3}+\frac{4\times1}{9\times1}=\frac{3}{9}+\frac{4}{9}

Finally we'll combine and obtain the following:

3+49=79 \frac{3+4}{9}=\frac{7}{9}

Answer

79 \frac{7}{9}

Exercise #20

Solve the following equation:

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

Video Solution

Step-by-Step Solution

We must first identify the lowest common denominator between 4 and 8.

In order to determine the lowest common denominator, we need to find a number that is divisible by both 4 and 8.

In this case, the common denominator is 8.

We will then proceed to multiply each fraction by the appropriate number to reach the denominator 8.

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

1×24×2+5×18×1=28+58 \frac{1\times2}{4\times2}+\frac{5\times1}{8\times1}=\frac{2}{8}+\frac{5}{8}

Finally we'll combine and obtain the following:

2+58=78 \frac{2+5}{8}=\frac{7}{8}

Answer

78 \frac{7}{8}