Modern nutritionists use body mass index to judge human health, which is equal to the quotient of the square of weight (kg) and height (m). Healthy people's body mass index is between 20 and 25. Body mass index is lower than 18, which belongs to unhealthy thinness; A body mass index higher than 30 is unhealthy and obese.

(1) Let a person's mass be W (kg) and height be H (m), and find his body mass index;

(2) Teacher Zhang is 1.75m in height and 60kg in mass. Find his body mass index;

(3) Calculate the parents' body mass index (rounded to the whole number)

A person's heart rate during exercise is usually related to his/her age. If A can represent his/her age and B can represent the maximum number of heartbeats he/she can bear during normal exercise, then b=0.8(220-a).

(1) Under normal circumstances, what is the maximum number of heartbeats a teenager of 14 can bear during exercise?

(2) A 45-year-old male has a heartbeat of 22 times at 10 second during exercise. Is he in danger?

Zhang Yu's height1.2m. At a certain moment, the length of his shadow is 2m/

(1) What is the height of Zhang Yu at this time?

(2) If l is used to represent the shadow length of an object, how can algebraic expressions be used to represent the height of the object here and now?

(3) The shadow length of buildings in this area is 5.5m.. What is its height at this time?