LEARN MATH STEP BY STEP THROUGH VERY EASY PROCESS

AVERAGE

**Average**

**The average is of two or more similar quantities is the
quantity obtained by dividing the sum of the quantities by the number of
quantities. Another term is used for Average which is “Arithmetic Means”**

** The sum of the
quantities**

** Average = ------------------------------------------**

** The number of the quantities**

**So, The sum of the quantities = Average X The number of the
quantities**

**There is some important note, in the time of addition of the
quantity the unit should be the same but the time of division unit may differ.**

**Example-**

**1) The number of
student attending a class during a week were Monday- 35, Tuesday-42, Wednesday-
48, Thursday – 37, Friday – 40 and Saturday – 38. Find the average daily
attendance.**

**Ans.) We can see
that, according to the daily attendance of student like this –**

**
Monday – 35**

**
Tuesday – 42**

**
Wednesday – 48**

** Thursday – 37**

**
Friday – 40**

**
Saturday – 38**

** So, weekly
(Monday to Saturday) attendance = (35 + 42 + 48 + 37 + 40 + 38) students**

** Total days
from Monday to Saturday = 6 days**

** Total
student attendance**

** Average
attendance = ---------------------------------**

** Total number of days**

** 35 + 42 + 48 + 37 + 40 + 38 240**

** Average
attendance = -------------------------- = -------**

** 6 6**

** = 40 students (Ans.)**

**2) If 7 books
cost $ 30 each and 3 books cost $ 40 each, then find the average cost of the books ?**

**Ans.) 7 books
cost $ 30 each, so total cost of
7 books = 30 X 7 = $ 210**

** 3
books cost $ 40 each, so total
cost of 3 books = 40 X 3 = $ 120**

** Total number of
books = 7 + 3 = 10 books**

** Total costing
to purchase all these 10 books = 210 + 120 = $ 330**

** 330**

** So, the
average cost of books are = ---------- = $ 33 **

** 10**

**The average cost of the books is** **$ 33 (Ans.)**

**3) The average age of 6 persons is 14.5 years, the average
age of 4 of them is 13.25 years. If the age of the fifth person is 16 years find
the age of the sixth person.**

**Ans.) The average age
of 6 person is 14.5 years, so the total age of the 6 person is 14.5 X 6 = 87 years**

**As per the
given condition, the average age of 4 of them is 13.25 years, so the total age
of the first 4 persons is = 13.25 X 4 = 53 years **

**If the age of fifth person is 16 years, then the age of sixth person
is = Total age of 6 person – (total age
of 4 person + age of fifth person)**

**So, 87 – ( 53 + 16)
= 87 – 69 = 18 years**

**The age of Sixth person is 18 years (Ans.)**

**4) The average weight of 10 students in a class is 53 kg.
when the weight of the teacher is added, the average weight goes up by 2 kg. find
the weight of the teacher**

**Ans.) The average
weight of 10 students in a class is 53 kg,**

** so the total weight
of 10 students is = 53 X 10 = 530 kg**

**if the weight of a teacher has been added then the average
weight of students with teacher is increased by 2 kg, hence the average weight
of 11 people is 53 + 2 = 55 kg.**

**So, total weight of 11 people is = 55 X 11 = 605**

**The weight of the teacher is = total weight of 11 people –
total weight of 10 people ****= 605 – 530 = 75 kg**

** The weight of the
teacher is 75 kg (Ans.)**