According to the conversion of 1 m =3 feet, we can know that 1 foot is about 33.33cm (two decimal places are reserved).
The substitution formula is: height (cm)÷2- 13(cm)= 1.9? × 33.33 cm
So the height is about: 152.65cm?
Follow? 5% is the normal range: the waist circumference is normal between 145 cm and 160 cm;
To sum up, if your height is between 145 cm and 160 cm, then the waist circumference 1' 9 belongs to the normal range;
If your height is below 145cm; ; Slightly thicker waist; (Height 145cm or more, this waist circumference is normal)
In junior high school, all aspects of the body are not fully developed. As long as the waist circumference is within this calculation method, don't worry!