I don’t know how do you do ratios problems in math but let me tell you how do I calculate ratios. I adopt a simple approach to finding ratios that ensures solving ratio problems without any mistake. I follow 5-steps method for calculating ratios.

- Read math ratio problem carefully
- Under line “to”, it tells which number is to be taken as denominator or numerator
- In medium to hard questions, “to” is not given, then under line the item with reference of which ratio is to be calculated.
- These reference numbers may be more than one, it means that I’ve to find more than one ratios in the same ratio mat problem.
- Calculate all ratios by reducing them to their lowest terms to find final ratio.

**How do you do ratios problems? | How do I calculate ratios? – Example 1**

What is ratio of 30 to 45?

Solution

Read carefully the ratio problem and underline “to”. Now the number that follows “to” will be denominator and the number the precedes “to” will be numerator. Now write ratio 30 to 45 as 30/45. Reduce it to the lowest term 2/3. This is answer.

**How do you do ratios problems? | How do I calculate ratios? – Example 2**

**How do you do ratios problems? | How do I calculate ratios? – Example 2**

In a class, 30% of girls have brown eyes, and 50% of boys have brown eyes. If the ratio of the boys to the girls in class is 5:3, then what is the fraction of the students in the class have brown eyes?

(A) 13/60

(B) 14/75

(C) 17/40

(D) 17/50

(E) 29/59

Solution

Read last sentence of the math problem carefully. Here “fraction” means “ratio” and “in the class” means “to the class”. Now the sentence will read as “what is the (ratio) of the students (to) the class having brown eyes?” So we have to calculate ratio with reference to the class.You have to determine following two parameters

- Total brown-eyed students
- Total class size

But class size is unknown. Assume class size = 80

How do you do ratios problems? By assuming 100?

In fact, you may assume 100 or any number but see boys to girls ratio in the class is 5:3. So add them 5:3 (5+3 = 8). For simplicity of calculations I assume 8 x 10 = 80. This is how do I calculate ratios

Total number of boys = 5/8 x 80 = 50

Total number of girls = 3/8 x 80 = 30

30 % of girls having brown eyes = 30/100 x 30 = 9

50% of boys having brown eyes = 50/100 x 50 = 25

Total students having brown eyes = 9 + 25 = 34

Now find the fraction (ratio) of brown-eyed students **to** the class

= 34/80

= 17/40 (after reducing to lowest term)

Answer is (C)

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