Average Formulas
average = (sum of the items)/(number of items)
Notice, we can also write this as:
sum of items = (average)*(number of items)
This latter form can be powerful. For example, if we add or subtract one item from a set, we can easily figure out how that changes the sum, and that can allow us to calculate the new average. Also, if we are combining two groups of different sizes, we can’t add averages, but we can add sums.
Practice Questions: Averages
Question 1
There are 36 boys and 44 girls in a class. The average score of boys is 40 points and girls is 35 points. Then what will be the average score of the class?
a) 37.25 points b) 28.95 points c) 35.5 points d) 40.04 points
Answer : a) 37.25 points
Solution:
Average score of 36 boys = 40 points
Total score of 36 boys = 36 x 40 = 1440
Average score of 44 girls = 35 points
Total score of 44 girls = 35 x 44 = 1540
Total score of(36+44)80 Students = 1440 + 1540 = 2980 points
Average score of the whole class = (2980 / 80) = 37.25
Hence the required answer is 37.25 points.
Question 2
The average weight of kids in a home is 16 kg and adults is 35 kg. Find the average weight of all the person in home.
a) 25.5 kg b) 25 kg c) none of these d) cannot be determined
Answer : d) cannot be determined
Solution :
From the question, we can say that the data given is inadequate because the number of adults or kids is not mentioned in the question.
