Understanding Body Mass Index (BMI) Calculation

Body Mass Index (BMI) is a measure used to assess a person's weight in relation to their height. It is a widely used indicator of whether a person has a healthy weight for their height. Calculating BMI involves a simple formula using metric units.

BMI Formula Using Metric Units

The standard formula for calculating BMI using metric measurements is:

$\text{BMI} = \frac{\text{Weight (kg)}}{\text{Height (m)}^2}$

Where:

• Weight is measured in kilograms (kg).
• Height is measured in meters (m).

Calculating BMI Step-by-Step

Let's apply the BMI formula to the given problem.

Given Information:

• Weight = 90 kg
• Height = 170 cm

Step 1: Convert Height to Meters

The height is given in centimeters (cm), but the formula requires height in meters (m). We need to convert 170 cm to meters. There are 100 cm in 1 meter.

Height in meters = $\frac{\text{Height in cm}}{100}$

Height in meters = $\frac{170}{100}\text{ m} = 1.70\text{ m}$

Step 2: Apply the BMI Formula

Now we can plug the weight in kilograms and the height in meters into the BMI formula:

$\text{BMI} = \frac{\text{Weight (kg)}}{\text{Height (m)}^2}$

$\text{BMI} = \frac{90\text{ kg}}{(1.70\text{ m})^2}$

Step 3: Calculate the Squared Height

Calculate the square of the height in meters:

$(1.70\text{ m})^2 = 1.70 \times 1.70\text{ m}^2 = 2.89\text{ m}^2$

Step 4: Perform the Final Division

Now, divide the weight by the squared height:

$\text{BMI} = \frac{90\text{ kg}}{2.89\text{ m}^2}$

$\text{BMI} \approx 31.14186...\text{ kg/m}^2$

Rounding the result to two decimal places gives us approximately 31.14 kg/m².

Comparing Result with Options

The calculated BMI is approximately 31.14 kg/m². Let's look at the provided options:

• 30.41 kg/m²
• 31.14 kg/m²
• 32.16 kg/m²
• 32.71 kg/m²

Our calculated value matches the second option.

Revision Table: BMI Calculation Key Points

Additional Information on BMI and Health Categories

BMI is a screening tool and not a diagnostic tool. It provides an estimate of body fat for most people and can be used to identify weight categories that may lead to health problems. Here are the standard BMI categories for adults:

Based on the calculated BMI of 31.14 kg/m², the person falls into the Obesity (Class I) category according to this classification. It's important to remember that BMI interpretation can vary based on factors like age, sex, muscle mass, and ethnicity.