COMPARISON OF RATIOS

To compare two ratios, write them as fractions.

Case 1 :

After writing the given ratios as fractions, if the denominators are same, compare the numerators. The fraction with greater numerator is greater in value.

Case 2 :

After writing the given ratios as fractions, if the denominators are different, make the denominators same using the least common multiple of the denominators.

After making the denominators same, compare the numerators. The fraction with greater numerator is greater in value.

Example 1 :

Compare 2 : 3 and 5 : 3.

Solution :

2 : 3 = 2/3

5 : 3 = 5/3

The fractions 2/3 and 5/3 have the same denominator.

Compare the numerators.

2 < 5

So, 

2/3 < 5/3

2 : 3 < 5 : 3

Example 2 :

Compare 3 : 5 and 4 : 7.

Solution :

3 : 5 = 3/5

4 : 7 = 4/7

The fractions 3/5 and 4/7 do not have the same denominator.

Least common multiple of the denominators (5, 7) = 35.

Make the denominators of the fractions as 35 using multiplication.

3/5 = (3x7/5x7) = 21/35

4/7 = (4x5/7x5) = 20/35

The fractions 21/35 and 20/35 have the same denominator.

Compare the numerators.

21 > 20

So,

21/35 > 20/35

3/5 > 4/7

3 : 5 > 4 : 7

Example 3 :

Compare 3 : 4 and 5 : 6.

Solution :

3 : 4 = 3/4

5 : 6 = 5/6

The fractions 3/4 and 5/6 do not have the same denominator.

Least common multiple of the denominators (4, 6) = 12.

Make the denominators of the fractions as 35 using multiplication.

3/4 = (3x3/4x3) = 9/12

5/6 = (5x2/6x2) = 10/12

The fractions 9/12 and 10/12 have the same denominator.

Compare the numerators.

9 < 10

So,

9/12 < 10/12

3/4 < 5/6

3 : 4 < 5 : 6

Example 4 :

Compare 1.2 : 1.5 and 2 : 5.

Solution :

1.2 : 1.5 = 1.2/1.5

= (1.2x10)/(1.5x10)

= 12/15

= 4/5

2 : 5 = 2/5

The fractions 4/5 and 2/5 have the same denominator.

Compare the numerators.

4 > 2

So, 

4/5 < 2/5

1.2 :  1.5 > 2 : 5

Example 5 :

Compare 1 : 2.5 and 1.5 : 4.5.

Solution :

1 : 2.5 = 1/2.5

= (1x10)/(2.5x10)

= 10/25

= 2/5

1.5 : 4.5 = 1.5/4.5

= (1.5x10)/(4.5x10)

= 15/45

= 1/3

The fractions 2/5 and 1/3 do not have the same denominator.

Least common multiple of the denominators (5, 3) = 15.

Make the denominators of the fractions as 35 using multiplication.

2/5 = (2x3/5x3) = 6/15

1/3 = (1x3/3x5) = 3/15

The fractions 6/15 and 3/15 have the same denominator.

Compare the numerators.

6 > 3

So,

6/15 > 3/15

2/5 > 1/5

1 : 2.5 > 1.5 : 4.5

Example 6 :

Compare 2⅓ : 3 and 3.6 : 4.8.

Solution :

⅓ : 3  = 7/3 : 10/3

= 7 : 10

= 7/10

3.6 : 4.8 = 3.6/4.8

= 36/48

= 3/4

The fractions 7/10 and 3/4 do not have the same denominator.

Least common multiple of the denominators (10, 4) = 20.

Make the denominators of the fractions as 20 using multiplication.

7/10 = (7x2/10x2) = 14/20

3/4 = (3x5/4x5) = 15/20

The fractions 14/20 and 15/20 have the same denominator.

Compare the numerators.

14 < 15

So,

14/20 < 15/20

7/10 < 3/4

2⅓ : 3  < 3.6 : 4.8

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