Thirty women were examined in a hospital by a doctor and the number of heart beats per minute recorded and summarised as follows. Find the mean heart beats per minute for these women, choosing a suitable method. `Heart beats` (per min.)    65-68   68-71   71-74   74-77   77-80   80-83   83-86 No. of women:  2           4          3           8         7            4          2

Thirty women were examined in a hospital by a doctor and the number of heart beats per minute were recorded and summarised as follows. Find the mean heart beats per minute for these women, choosing a suitable method.

The number of students absent in a class were recorded every day for 120 days and the information is given in the following frequency table: No. of students absent (x) : 0 1 2 3 4 5 6 7 No. of days (f) : 1 4 10 50 34 15 4 2 Find the mean number of students absent per day.

A certain drug raises a patient's heart rate, h, in beats per minute, according to the equation h(x)=65+0.2x , where x is the number of milligrams of the drug in the patient's bloodstream. After t hours, the level of the drug in the patient's bloodsteam decrease exponentially according to the equation x(t)=512(0.7)^(t) . After 5 hours, what is the number of beats per minute in the patient's heart rate, correct to the nearest whole number?