TS Polycet (Polytechnic) 2015 Previous Question Paper with Answers And Model Papers With Complete Analysis

11)The equation of the line passing through (0, 0) and (a cosα, b sinα) is

A) ay – bx tan α

B) by = ax tan α

C) by = – ax tan α

D) ay = – bx tan α

View Answer

A) ay – bx tan α
Explanation:Let A(0, 0), B(a cos a, b sin a)
The equation of \overline{AB} is
Y – y1 = \frac{Y_2-Y_1}{X_2-X_1}(X-X_1)
Y – 0 = \frac{b\;\sin\alpha-0}{a\;\cos\alpha-0}(X-0)
Y = \frac{b\;\sin\alpha}{a\;\cos\alpha}X
⇒Y = b/a tanα x⇒ ay = bx tanα

12)The area of the triangle formed by (a, b + c), (b, c + a) and (c, a + b) is

A) a + b + c sq. units

B) abc sq. units

C) (a + b + c)2 sq. units

D) 0 sq. units

View Answer

D) 0 sq. units
Explanation:Bet A(a, b + c), B(b, c + a), c(c, a + b)
The area of the triangle ΔABC
= \frac12\begin{vmatrix}X_1-X_2&Y_1-Y_2\\X_1-X_3&Y_1-Y_3\end{vmatrix}
= \frac12\begin{vmatrix}a-b&b+c-c-a\\a-c&b+c-a-b\end{vmatrix}
= \frac12\begin{vmatrix}a-b&b-a\\a-c&c-a\end{vmatrix}
= \frac12\left|(a-b)\;(c-a)-(b-a)(a-c)\right|
= \frac12\left|\cancel{ac}-\cancel{a^2}-\cancel{bc}+\cancel{ab}-\cancel{ab}+\cancel{bc}+\cancel{a^2}-\cancel{ac}\right|=0

13)The nearest point from the origin is

A) (2, -1)

B) (3, -1)

C) (5, 0)

D) (2, -3)

View Answer

A) (2, -1)
Explanation:Verify options O (0, 0)
1) O (0,0), (2,-1) ⇒ \sqrt{4+1} = √5
2) O (0,0), (3,-1) ⇒ \sqrt{9+1}=√10
3) O (0, 0), (5, 0) ⇒\sqrt{25+0}=√25
4) O (0, 0), (2, -3) ⇒ \sqrt{4+9}=√13

14)If the points (a, 0), (0, b) and (1, 1) are collinear, then \frac1a+\frac1b=

A) -1

B) 2

C) 0

D) 1

View Answer

D) 1
Explanation:Let A (a, 0), B (0, b), C(1, 1)
Slope of \overline{AB} = slope of \overline{BC}
\frac{b-0}{0-a}=\frac{1-b}{1-0}\Rightarrow\frac b{-a}=\frac{1-b}1\Rightarrow\frac{-b}a=1-b
\frac1b+\frac1a=1
\frac1a+\frac1b=1

15)The equation of a straight line passing through the points (4, -7) and (1, -5) is

A) 2x + 3y-13 = 0

B) 2x-3y+ 13 = 0

C) 2x + 3y+13 = 0

D) 2x-3y-13 = 0

View Answer

C) 2x + 3y+13 = 0
Explanation:Let A(4,-7), B (1, – 5) Equation of \overline{AB} is Y-Y_1\;=\frac{Y_2-Y_1}{X_2-X_1}(X-X_1)
Y+7\;=\frac{-5+7}{1-4}(X-4)
Y+7 = 2/3 (x-4)
-3y-21 = 2x-8
⇒2x+3y+13 = 0

16)The slope of the line which is parallel to 3x – 2y + 1 = 0 is

A) -3/2

B) 3/2

C) 2/3

D) -2/3

View Answer

B) 3/2
Explanation:Slope of the line 3x – 2y + 1 = 0 is
M = -a/b = -3/-2 = 3/2
Slope of the parallel line = m = 3/2

17)In an equilateral triangle ABC if AD ⊥ BC, then AD2=

A) 2CD2

B) 3 CD2

C) 4 CD2

D) 5 CD2

View Answer

B) 3 CD2
Explanation:ΔABC, is an equilateral triangle, AD-height and side ‘a’ units.
Height h units

In ΔABD, ΔACD
∠B = ∠C (∴60°)
∠ADB = ∠ADC (∴90°)
∠BAD = ∠DAC
(∴Sum of the angles property) and BA = CA.
∴∠ABD = ∠ACD (∴SAS congruence condition)
BD = CD = 1/2 BC = a/2 (∴ C.P.C.T.)
ΔABD, AB2 = AD2 + BD2 (∴Pythagoras theorem)
A2 = h2 +(a/2) 2 a2 = h2 +a2/4
h2 = 4a2-a2/4 = 3a2/4
⇒4h2 = 3a2 ⇒ 4(AD)2 = 3(BC)2
⇒ 4(AD)2 = 3(2 CD)2
⇒ 4(AD)2 = 3 x 4 CD2
⇒ 4(AD)2 = 12 CD2
⇒ (AD)2 = 12CD2/4 = 3CD2

18)The areas of two similar triangles are 121 cm2 and 64 cm2 respectively. If the median of the first triangle is. 12.1 cm, then the corresponding median of the other triangle is

A) 11 cm

B) 8.1 cm

C) 11.1 cm

D) 8.8 cm

View Answer

D) 8.8 cm
Explanation:
ΔABC/ΔXYZ = AD2/XW2
121/64 = (12.1)2/XW2 ⇒121/64 = 146.41/XW2
XW2 = 146.4×64/121 = 77.44
XW = √77.44 = 8.8 cm

19)If in two triangles ABC and DEF, \frac{AB}{DE}=\frac{BC}{FE}=\frac{CA}{FD}, then

A) ΔFDE ∼ ΔCAB

B) ΔFDE ∼ ΔABC

C) ΔBCA ∼ ΔFDE

D) None

View Answer

C) ΔBCA ∼ ΔFDE
Explanation:
\frac{AB}{DE}=\frac{BC}{FE}=\frac{CA}{FD}
⇒ ΔBCA ∼ ΔFDE

20)If the ratio of perimeters of two similar triangles is 9 : 16, then the ratio of their altitudes is

A) 16 : 9

B) 3 : 4

C) 9 : 16

D) 4 : 3

View Answer

C) 9 : 16
Explanation:P1/h1 ⇒ 9/16= h1/h2
H1/h2 =9:16
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