NCERT Solutions for Class 9 Maths Chapter 7 Triangles Ex 7.5 are part of NCERT Solutions for Class 9 Maths. Here we have given NCERT Solutions for Class 9 Maths Chapter 7 Triangles Ex 7.5.

- Triangles Class 9 Ex 7.1
- Triangles Class 9 Ex 7.2
- Triangles Class 9 Ex 7.3
- Triangles Class 9 Ex 7.4
- Triangles Class 9 Ex 7.5

Board |
CBSE |

Textbook |
NCERT |

Class |
Class 9 |

Subject |
Maths |

Chapter |
Chapter 7 |

Chapter Name |
Triangles |

Exercise |
Ex 7.5 |

Number of Questions Solved |
4 |

Category |
NCERT Solutions |

## NCERT Solutions for Class 9 Maths Chapter 7 Triangles Ex 7.5

Question 1.

ABC is a triangle. Locate a point in the interior of Δ ABC which is equidistant from all the vertices of Δ ABC.

Solution:

Let OD and OE be the perpendicular bisectors of sides BC and CA of Δ ABC.

∴ 0 is equidistant from two ends B and C of line-segment BC as 0 lies on the perpendicular bisector of BC.

Similarly, 0 is equidistant from C and A. Thus, the point of intersection 0 of the perpendicular bisectors of sides BC, CA and AB is the required point.

Question 2.

In a triangle locate a point in its interior which is equidistant from all the sides of the triangle.

Solution:

Let BE and CF be the bisectors of ∠ABC and ∠ACB respectively intersecting AC and AB at E and F respectively.

Since 0 lies on BE, the bisector of ∠ABC, hence O will be equidistant from AB and BC. Again, O lies on the bisector CF of ∠ACB. Hence, 0 will be equidistant from BC and AC. Thus, 0 will be equidistant from AB, BC, and CA.

Question 3.

In a huge park, people are concentrated at three points (see figure)

A.where there are different sides and swings for children

B. near which a man-made lake is situated

C. which is near to a large parking and exit.

Where should an ice-cream parlor be set up so that maximum number of persons can approach it?

[Hint: The parlor should be equidistant from A, B and C.]

Solution:

The ice-cream parlor should be equidistant from A, B, and C for which the point of intersection of perpendicular bisectors of AB, BC, and CA should be situated.

So, 0 is the required point which is equidistant from A, B, and C.

Question 4.

Complete the hexagonal and star shaped Rangolies [see fig. (i) and (ii)] by filling them with as many equilateral triangles of side 1 cm as you can. Count the number of triangles in each case. Which has more

Solution:

We first divide the hexagon into six equilateral triangles of side 5 cm as follows:

We take one triangle from six equilateral triangles as shown above and ‘ make as many equilateral triangles of one side 1 cm as shown in the figure given below.

The number of equilateral triangles of side 1cm = 1+ 3 + 5 + 7 + 9 = 25

So, the total number of triangles in the hexagon = 6 x 25 = 150.

To find the number of triangles in Fig. (ii), we adopt the same procedure.

So, the number of triangles in Fig. (ii) = 12 x 25 = 300 Hence, Fig. (ii) has more triangles.

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