What is the formula to calculate the average of a set of numbers?

If the average of a group of numbers is 25 and there are 4 numbers, what is the total sum of these numbers?

Total sum 
= Average × Number of numbers 
= 25 × 4 
= 100

True or False: The average of a set of numbers can be greater than the largest number in that set.

False. The average cannot be greater than the largest number.

How do you find the missing number if the average of five numbers is 20 and four numbers are 18, 22, 20, and 25?

What is the weighted average if a student scores 80, 90, and 70 in exams weighted 20%, 50%, and 30%?

Fill in the blank: The formula to calculate average speed when speeds vary over equal distances is ___

If a runner runs 1 hour at 10 km/h and 1 hour at 14 km/h, what is their average speed?

What happens to the average when a new number is added to a set?

Calculate the new average if the average of 10 numbers is 30 and number 40 is added.

True or False: When some observations are removed, the new average can be calculated by 

True.

Example: Average of 20 students is 45. If 5 students with an average of 50 are removed, what is the new average?

Fill in the blank: The formula for calculating combined average is ___

If the average of a group of numbers is 15 and the sum of known numbers is 60 for 4 numbers, what is the missing number?

Missing number = (Average × Number of values) - Sum of known values 
= (15 × 5) - 60 
= 75 - 60 
= 15

What is the average speed if a car travels 60 km at 40 km/h and returns at 60 km/h?

True or False: The arithmetic mean of speeds is used when calculating average speed over equal time intervals.

True.

If the average of a group is 30 and the total number of elements is 10, what is the total sum?

Total sum = Average × Total elements 
= 30 × 10 
= 300

Calculate the new average if the average of 8 numbers is 20 and one number 24 is removed.