Triangle Word Problems

**Page 1**

1.

A, B and C are the mid points of the three sides of ΔPQR as shown in the figure. QB and CR intersect at G. If QD = 5 cm, find the length of GD.

a. | $\frac{5}{3}$units | ||

b. | 3 units | ||

c. | 2 units | ||

d. | $\frac{8}{5}$units |

[A and C are midpoints of QR and PQ.]

QB = 10

[QD = 5, Ratio of the sides of the similar triangles is 2.]

QG = 10 ×

[G is the point of intersection of the medians, which divides the median in 2 : 1 ratio.]

GD = QG - QD =

Correct answer : (1)

2.

$\angle $DAC = 40^{o}, find $\angle $FBC.

a. | 25 ^{o} | ||

b. | 20 ^{o} | ||

c. | 50 ^{o} | ||

d. | 40 ^{o} |

[From the figure.]

180

[Substitute and simplify.]

In ΔBFC,

[From the figure.]

[Substitute and simplify.]

Correct answer : (4)

3.

If AD = 4 cm, CF = 3 cm, then what is the length of AC?

a. | 2$\sqrt{5}$ cm | ||

b. | 5$\sqrt{7}$ cm | ||

c. | 5 cm | ||

d. | 6$\sqrt{3}$ cm |

[Applying Apollonian theorem.]

(AB

[Add the above two equations.]

(AB

AC

[From the figure, DC =

3AC

3AC

[Simplify.]

[Take the square root.]

Correct answer : (1)

4.

What is the point of concurrency of the medians of a triangle called?

a. | circumcenter | ||

b. | orthocenter | ||

c. | incenter | ||

d. | centroid |

[By definition.]

Correct answer : (4)

5.

Name the point of concurrency of the altitudes of a triangle.

a. | circumcenter | ||

b. | orthocenter | ||

c. | centroid | ||

d. | incenter |

[By definition.]

Correct answer : (2)

6.

In ΔABC, AD is the median and the area of the ΔABC is 36 cm^{2}. Find the area of ΔADC.

a. | 18 cm ^{2} | ||

b. | 6 cm ^{2} | ||

c. | 12 cm ^{2} | ||

d. | 16 cm ^{2} |

Area of ΔADC = Area of ΔADB =

[Step 1.]

Area of ΔADB =

[Substitute.]

Correct answer : (1)

7.

In ΔABC, what is the length of the median AD?

a. | 7$\sqrt{2}$ cm | ||

b. | 18 cm | ||

c. | 20 cm | ||

d. | 24 cm |

[By Apollonius Theorem.]

(15

[Substitute the values.]

450 + 800 = 2 [AD

[Simplify]

2 [AD

[Simplify.]

AD

[Divide by 2 on both sides.]

AD = 24 cm

[Take square root on both sides.]

Correct answer : (4)

8.

In ΔABC, AD is the median and G is the Centroid. AG : AD = ?

a. | 1 : 3 | ||

b. | 2 : 3 | ||

c. | 1 : 4 | ||

d. | 1 : 2 |

AG : GD = 2 : 1

[Step 1.]

AG : AD = 2 : 3

[Since AD = AG + GD = 2GD + GD = 3GD.]

Correct answer : (2)

9.

In what type of triangle at least one median coincides with an altitude?

a. | either isosceles or equilateral | ||

b. | isosceles | ||

c. | equilateral | ||

d. | right angled |

In an isosceles triangle, the median from the vertex containing the congruent sides is perpendicular to the base.

In an equilateral triangle, the median from any vertex to the opposite side will be perpendicular to that side.

So, in isosceles triangle and equilateral triangle, at least one median coincides with an altitude.

Correct answer : (1)

10.

Select the correct statement/statements.

1. In an equilateral triangle, orthocenter coincides with incenter.

2. In an equilateral triangle, median and angle bisector from a vertex are the same.

3. In an equilateral triangle, centroid coincides with circumcenter.

1. In an equilateral triangle, orthocenter coincides with incenter.

2. In an equilateral triangle, median and angle bisector from a vertex are the same.

3. In an equilateral triangle, centroid coincides with circumcenter.

a. | 2 only | ||

b. | 3 only | ||

c. | 1, 2, and 3 | ||

d. | 1 only |

So, centroid, orthocenter, incenter and circumcenter of an equilateral triangle coincide.

All the statements are correct.

Correct answer : (3)