There are 20 peoples in a singing group. The mean age of 12 of the members is 18years. The mean age of the remaining 8 is 23 years. What is the mean age of the 20 members of the singing group?

  20

Step-by-step explanation:

The sum of the ages of the first 12 is ...

  12×18 = 216

The sum of the ages of the remaining 8 is ...

  8×23 = 184

So, the sum of ages of all 20 people is ...

  216 +184 = 400

and their average age is ...

  400/20 = 20

The mean age of the members of the group is 20.

The mean of a data set is the total of the values, divided by the number of values.

1/5^2 = 7.56/45

step-by-step explanation:

12: 00 p.m. to 7: 00 p.m. is a total of 7 hours.

4: 00 p.m. to 7: 00 p.m. is a total of 3 hours.

this means that from 4: 00 p.m to 7: 00 p.m. this represents 3/7 of what was lost from 12: 00 p.m. to 7: 00 p.m.

after knowing this, after doing 11,600 - 6,800 = 4,800

4,800 represents 3/7 of what was lost for 7 hours.

we then divide 4,800 by 3 which gets 1,600.

because we know that 1,600 represents 1/7 of how much water was lost, we just have to multiply by 7, which gets 11,200.   after adding 11,200 to how much water was left at 7: 00 p.m. which was 6,800. 11,200 + 6,800 = 18,000

this means that the pool originally had 18,000 gallons in the pool.

you can also check your work by doing 18,000 - 4(1600), which becomes           1800 - 6400 which gets you 11,600.