Question

The average age of staff in the maths department is 40.

Answer 1

Answer:

Cerian is 28 years old

Step-by-step explanation:

The given parameters are;

The average age of the staffs in the mathematics department = 40

The number of staffs in the department = 7

The average age of Jill, Nicky and Wendy = 41

The average age of Andy, Alan and Cathy = 43

From the given parameters, we have;

The average age of the staffs in the mathematics department = (The sum total of the ages of the members of the math department)/(The number of staffs in the department)

Therefore;

40 = (The sum total of the ages of the members of the math department)/ (7)

From which we have;

The sum total of the ages of the members of the math department = 40 × 7 = 280

Which gives;

Jill's age + Nicky's age + Wendy's age + Cathy's age + Cerian's age + Alan's age + Andy's age = 280 years

The average age of Jill, Nicky and Wendy = 41

Given that Jill, Nicky, and Wendy make up 3 of the 7 members of staffs, we have;

The average age of Jill, Nicky and Wendy = (The sum total of the ages of Jill, Nicky, and Wendy)/(The number of staff Jill, Nicky, and Wendt make)

Therefore;

The sum total of the ages of Jill, Nicky, and Wendy = 41 × 3 = 123

Which gives;

Jill's age + Nicky's age + Wendy's age = 123 years

Similarly, the sum total of the ages of Andy, Alan, and Cathy = 43 × 3 = 129

Which gives;

Andy's age + Alan's age + Cathy's age = 129 years

Therefore;

Cerian's age = (Jill's age + Nicky's age + Wendy's age + Cathy's age + Cerian's age + Alan's age + Andy's age) - (Jill's age + Nicky's age + Wendy's age) + (Andy's age + Alan's age + Cathy's age)

∴ Cerian's age = 280 years - 123 years - 129 years = 28 years