Mathimat Class Seven Chapetar 8

Attempt all questions.
⦁ Define tabular form of set.   
If we list all elements of a set within the braces {   } and separate each element by using a comma “ ,” it is called the tabular or roster form.
For example; A = {a, e, I, o, u} , 
C = {3, 6, 9, ------- 99},
M = {football, hockey, cricket}

⦁ Define rational numbers. 
A number which can be written in the form   is called a rational number.
The set of rational numbers is denote by Q.
For example; 0, 4,  ̶  3,    etc are rational numbers.
⦁ Simplify  (47  ÷  4 5)  ×  22 
Solution:    (47  ÷  4 5)  ×  22 
= (4) 7 ̶  5   ×  22   = 4 2 ×  22   = (4 × 2)2  =   8 2  =   64
⦁ Find the value of m in the following proportion.
 : m = 0.55 : 0.27
        Solution:       



Product of means   = product of extremes
m ×  0.55  =  1.1 × 0.27
m ×  0.55  =  0.297
     m   =   0.297 ÷   0.55
  m =  0 .54




⦁ Simplify

 Solution: 






⦁ After 32 years from now, a boy will be 5 times as old as he was 8 years back. How old is the boy now?
Solution:  Suppose the age of the boy = x
                   After the 32 years age will be = x + 32
                   The age was 8 years back = x  -̶   8
                  According to the situation
                              x + 32 = 5 ( x ̶  8)
                               x + 32 = 5x  - 40
                               5x ̶   x =  40 + 32
4x = 72
X = 18 years
                         Thus the boy is 18 years old.
⦁ Define the following terms. 
Radius:    The distance between the centre and any point on the circle is called radius.

Diameter:  A line segment that passes through the centre of a circle and touches two points on its edge is called the diameter of the circle.

Chord: A line segment joining two points on a circle is called the chord.