There are 9 boys and 6 girls in a hall, each holding coins in their hand. The mean number of coins for the children is 18 The mean number of coins for the boys is 14 Work out the mean number of coins for the girls.

24

Step-by-step explanation:

Average = total number of coins / number of students

If the mean number of coins with boys is 14, the total number of coins held by boys =  14 x 9 = 126

The total number of coins held by the students = total number of children x average number of coins held by the children

15 x 18 = 270

The total number of coins held by girls = 270 - 126 =144

The mean  number of coins for the girls = 144 / 6 = 24

reduce the friction between its moving parts

step-by-step explanation:

in fact, by reducing the friction between the moving parts of the machine, it is possible to reduce the energy wasted due to this friction; therefore, more input energy is converted into useful work, and this will improve the efficiency of the machine.

c

step-by-step explanation:

i think because what else can be a sample of every member