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 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}

Exercise #10

Solve the following equation:

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

Video Solution

Step-by-Step Solution

Let's first identify the lowest common denominator between 4 and 2.

In order to identify the lowest common denominator, we need to find a number that is divisible by both 4 and 2.

In this case, the common denominator is 4

We will then proceed to multiply each fraction by the appropriate number in order to reach the denominator 4

We'll multiply the first fraction by 1

We'll multiply the second fraction by 2

2×14×1+1×22×2=24+24 \frac{2\times1}{4\times1}+\frac{1\times2}{2\times2}=\frac{2}{4}+\frac{2}{4}

Finally we will combine and obtain the following:

2+24=44=1 \frac{2+2}{4}=\frac{4}{4}=1

Answer

1 1

Exercise #11

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 #12

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 #13

Solve the following equation:

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

Video Solution

Step-by-Step Solution

Let's begin by identifying 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.

Let's proceed to multiply each fraction by the appropriate number in order to reach the denominator 6.

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

2×23×2+1×16×1=46+16 \frac{2\times2}{3\times2}+\frac{1\times1}{6\times1}=\frac{4}{6}+\frac{1}{6}

Finally we'll combine and obtain the following result:

4+16=56 \frac{4+1}{6}=\frac{5}{6}

Answer

56 \frac{5}{6}

Exercise #14

Solve the following equation:

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

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

Finally we'll combine and obtain the following:

4+18=58 \frac{4+1}{8}=\frac{5}{8}

Answer

58 \frac{5}{8}

Exercise #15

Solve the following equation:

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

Video Solution

Step-by-Step Solution

We must first identify the lowest common denominator between 5 and 10.

In order to determine the lowest common denominator, we need to find a number that is divisible by both 5 and 10.

In this case, the common denominator is 10.

We will proceed to multiply each fraction by the appropriate number to reach the denominator 10.

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

1×25×2+6×110×1=210+610 \frac{1\times2}{5\times2}+\frac{6\times1}{10\times1}=\frac{2}{10}+\frac{6}{10}

Finally we'll combine and obtain the following:

2+610=810 \frac{2+6}{10}=\frac{8}{10}

Answer

810 \frac{8}{10}

Exercise #16

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 #17

Solve the following equation:

34+18= \frac{3}{4}+\frac{1}{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'll 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

3×24×2+1×18×1=68+18 \frac{3\times2}{4\times2}+\frac{1\times1}{8\times1}=\frac{6}{8}+\frac{1}{8}

Finally we'll combine and obtain the following:

6+18=78 \frac{6+1}{8}=\frac{7}{8}

Answer

78 \frac{7}{8}

Exercise #18

Solve the following equation:

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

Video Solution

Step-by-Step Solution

We must first identify the lowest common denominator between 4 and 12.

In order to determine the lowest common denominator, we need to find a number that is divisible by both 4 and 12.

In this case, the common denominator is 12.

We will then proceed to multiply each fraction by the appropriate number to reach the denominator 12.

We'll multiply the first fraction by 3

We'll multiply the second fraction by 1

1×34×3+6×112×1=312+612 \frac{1\times3}{4\times3}+\frac{6\times1}{12\times1}=\frac{3}{12}+\frac{6}{12}

Finally we'll combine and obtain the following:

3+612=912 \frac{3+6}{12}=\frac{9}{12}

Answer

912 \frac{9}{12}

Exercise #19

Solve the following equation:

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

Video Solution

Step-by-Step Solution

We must first identify the lowest common denominator between 6 and 12.

In order to determine the lowest common denominator, we need to find a number that is divisible by both 6 and 12.

In this case, the common denominator is 12.

We will then proceed to multiply each fraction by the appropriate number to reach the denominator 12.

We'll multiply the first fraction by 2

We'll multiply the second fraction by 1

2×26×2+4×112×1=412+412 \frac{2\times2}{6\times2}+\frac{4\times1}{12\times1}=\frac{4}{12}+\frac{4}{12}

Finally we'll combine and obtain the following:

4+412=812 \frac{4+4}{12}=\frac{8}{12}

Answer

812 \frac{8}{12}

Exercise #20

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}