Hello Everyone welcome to UTUG Education. We will see the solution of Composite Mathematics class 7th by S.K. Gupta and Anubhuti Gangal of S.Chand School Publication.
This is your Chapter – 8 , Ratio and Proportion and Unitary method of the book this is the part of Commercial Arithmetic unit which is your 3 unit of the book.
Key Facts:-
- A ratio is formed when two quantities are compared by division, i.e. a : b or a/b
- A ratio has no units.
- An equality of two ratios is called a proportion.
- Usually a ratio is written in its simplest form.
- The first and fourth terms of a proportion are called extremes and second and third terms are called means.
- Four quantities a, b, c and d are said to be in proportion if a : b = c : d ⇒ a / b = c / d ⇒ ad = bc, i.e., Product of extremes = Product of means.
- In a proportion a : b :: c : d, d is called the fourth proportional.
- Three quantities a, b, c are said to be continued proportion if a : b = b : c or a / b = b / c i.e. b² = ac
- In a continued proportion a : b :: b : c. b is called the mean proportional between a and c and c is called the third proportional.
- The method in which the value of a unit quantity is first calculated to find the value of any required quantity is called unitary method.
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