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A person’s Body Mass Index (BMI) is given by the following formula: BMI = \( \frac{w}{h^2} \) where \( w \) is their weight in kg, and \( h \) is their height in metres - Junior Cycle Mathematics - Question 1 - 2017

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A-person’s-Body-Mass-Index-(BMI)-is-given-by-the-following-formula:--BMI-=-\(-\frac{w}{h^2}-\)--where-\(-w-\)-is-their-weight-in-kg,-and-\(-h-\)-is-their-height-in-metres-Junior Cycle Mathematics-Question 1-2017.png

A person’s Body Mass Index (BMI) is given by the following formula: BMI = \( \frac{w}{h^2} \) where \( w \) is their weight in kg, and \( h \) is their height in m... show full transcript

Worked Solution & Example Answer:A person’s Body Mass Index (BMI) is given by the following formula: BMI = \( \frac{w}{h^2} \) where \( w \) is their weight in kg, and \( h \) is their height in metres - Junior Cycle Mathematics - Question 1 - 2017

Step 1

Geri's BMI Calculation

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Answer

To calculate Geri's BMI, we use the formula:

BMI=wh2BMI = \frac{w}{h^2}

Substituting in Geri's weight and height:

BMI=77.5(1.63)2=77.52.656929.2BMI = \frac{77.5}{(1.63)^2} = \frac{77.5}{2.6569} \approx 29.2

Thus, Geri's BMI is 29.2.

Step 2

Geri's New Weight Calculation

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Answer

To find Geri's new weight after losing weight with a BMI of 24.0, we use the formula again:

w=BMI×h2w = BMI \times h^2

Substituting the new BMI and Geri's height:

w=24.0×(1.63)2=24.0×2.656963.8 kgw = 24.0 \times (1.63)^2 = 24.0 \times 2.6569 \approx 63.8 \text{ kg}

Therefore, Geri's new weight is 63.8 kg.

Step 3

Comparison of Alex's and Jo's BMI

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Answer

Since Alex is 10 cm taller than Jo, let ( h_J ) be Jo's height in meters. Then Alex's height is ( h_A = h_J + 0.1 ) meters.

Both have the same weight ( w ). According to the BMI formula:

BMIJ=whJ2BMIA=w(hJ+0.1)2BMI_J = \frac{w}{h_J^2} \\ BMI_A = \frac{w}{(h_J + 0.1)^2}

To compare their BMIs, we note that as height increases, the denominator increases, hence:

BMIA<BMIJBMI_A < BMI_J

Thus, Alex’s BMI is less than Jo’s.

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