# NCERT Solutions for Class 12 Maths Chapter 7 Exercise 7.9

NCERT Solutions for Class 12 Maths Chapter 7 Exercise 7.9 Integrals in English Medium as well as हिंदी मीडियम free to download in PDF or view online without download updated for new academic session 2020-2021.

Download CBSE Apps based on Latest NCERT Solutions for 2020-21. Ask your doubts through discussion forum and discuss your Maths problems also with your friends.## NCERT Solutions for Class 12 Maths Chapter 7 Exercise 7.9

Class: | 12 |

Subject: | Maths |

Chapter 7: | Exercise 7.9 |

### 12th Maths Exercise 7.9 Solutions

NCERT Solutions for Class 12 Maths Chapter 7 Exercise 7.9 Integrals in English as well as Hindi Medium is given below updated for new session 2020-21. Download NCERT Books for class 12 all subject in Hindi and English Medium.

### Exercise 7.9 Solutions in Hindi & English

#### Questions from Board Papers

1. Let A = {1, 2, 3… 12} and R be a relation in A × A defined by (a, b) R (c, d) if ad = bc ∀ (a, b), (c, d) ∈ A × A. Prove that R is an equivalence relation. Also obtain the equivalence class [(3, 4)].

2. A trust invested some money in two type of bonds. The first bond pays 10% interest and second bond pays 12% interest. The trust received ₹ 2800 as interest. However, if trust had inter changed money in bonds, they would have got ₹ 100 less as interest using matrix method, find the amount invested in each bond by the trust.

3. If ‘*’ is a binary operation on R defined by a * b = a + b + ab. Prove that * is commutative and associative. Find the identify element. Also show that every element of R is invertible except –1.

##### Important Questions for Practice

1. Two tailors A and B earn ₹ 150 and ₹ 200 per day respectively. A can stitch 6 shirts and 4 pants per day, while B can stitch 10 shirts and 4 pants per day. How many days shall each work if it is desired to produce atleast 60 shirts and 32 pants at a minimum labour cost? Solve the problem graphically.

2. Let N denote the set of all natural numbers and R be the relation on N × N defined by (a, b) R (c, d) if ad (b + c) = bc (a + d). Show that R is an equivalence relation.

3. A man has ₹ 1500 to purchase two types of shares of two different companies S1 and S2. Market price of one share of S1is ₹ 180 and S2 is ₹120. He wishes to purchase a maximum of ten shares only. If one share of type S1 gives a yield of ₹ 11 and of type S2 yields ₹ 8 then how much shares of each type must be purchased to get maximum profit? And what will be the maximum profit?

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