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Aptitude Area Practice QA

1435.If the length of a rectangle is halved and its breadth is tripled, what is the percentage change in its area?
25 % Increase
25 % Decrease
50 % Decrease
50 % Increase
Explanation:

Let original length = 100 and original breadth = 100

Then original area = 100 × 100 = 10000

Length of the rectangle is halved

=> New length = $\dfrac{\text{Original length}}{2}=\dfrac{100}{2}=50$

Breadth is tripled

=> New breadth= Original breadth × 3 = 100 × 3 = 300

New area = 50 × 300 = 15000

Increase in area = New Area - Original Area = 15000 - 10000= 5000

Percentage of Increase in area = $\dfrac{\text{Increase in Area}}{\text{Original Area}} \times 100$

$=\dfrac{5000}{10000} \times 100=50\% $

44281.$\triangle$ABC is an equilateral triangle of side 14 cm. A semi circle on BC as diameter is drawn to meet AB at D, and AC at E. Find the area of the shaded region.
$49\left(\dfrac{\pi}{3}-\sqrt{3}\right)cm^{2}$
$49\left(\dfrac{\pi}{3}-\dfrac{\sqrt3}{2}\right)cm^{2}$
$49cm^{2}$
None
Explanation:

O is the centre of the circle and the mid-point of BC.DO is parallel to AC.

So, $\angle$DOB=$60^{o}$

Area of $\triangle$BDO=$\dfrac{49\sqrt{3}}{4}$

Area of sector OBD=$\dfrac{49\pi}{6}$

Hence area of the shaded region

=$2\left(\dfrac{49\pi}{6}-\dfrac{49\sqrt3}{4}\right)cm^{2}$

=$49\left(\dfrac{\pi}{3}-\dfrac{\sqrt3}{2}\right)cm^{2}$

44282.Through T, the mid-point of the side QR of a $\triangle$ PQR , a straight line is drawn to meet PQ produced to S and PR at U, so that PU=PS. If length of UR=2 units then the length of QS is
$2\sqrt{2}units$
$\sqrt{2} units$
2 units
5 units
Explanation:

We have QT=TR and PU=PS.UR=2 units

We draw RV $\parallel$ PS that meets SU extended at V.

In $\triangle$QST and $ \triangle$TVR

$\angle$QTS=$\angle$VTR [Opposite angles]

$\angle$QST=$\angle$TVR [Alternate angles as PS$\parallel$VR]

QT+TR

$\therefore\triangle$QST and $\triangle$TVR are congruent.

$\therefore$QS=VR -------- (i)

Now

$\angle$QST=$\angle$PUS=$\angle$VUR=$\angle$UVR

$\therefore$ In $\triangle$UVR

$\angle$VUR=$\angle$RVU

or,

RV=UR=2 -------- (ii)

From (i) and (ii)

QS=VR=UR=2units

44283.In the figure given below MN and NL are adjacent sides of a square and the arc MPL is drawn with N as centre and MN as radius. P is a point on the arc and PQRS is a square such that, RS, if extended, passes through L while RQ, if extended, passes through M. What is the ratio of the area of a square of side MN and the square PQRS?
$1:\left(3-2\sqrt{2}\right)$
$2:\left(3-2\sqrt{2}\right)$
$3:\left(3-2\sqrt{2}\right)$
$4:\left(3-2\sqrt{2}\right)$
Explanation:

It is given that RS passes through L and RQ passes through M.

On drawing the line RSL and RQM, the diagram shown above results. From the diagram, it is clear that MNLR has to be a square and P has to be the mid point of the arc.

As P is the mid-point of the arc, RN passes through P,

As NP is radius, it length is a.

Now,

RP=RN-NP, where RN is diagonal of the square with length $=\sqrt{a^2+a^2}=a\sqrt{2}$ and NP=a

Putting values,

RP=RN-NP

RP=$a\sqrt{2}-a$

RP=$a(\sqrt{2}-1)$

RP=$a\left(\sqrt{2}-1\right)$

where MN=PN=a

PQ=$\dfrac{RP}{\sqrt{2}}$

$a\sqrt{2}-a / \sqrt{2}$

$MN^{2}:PQ^{2}=2:3-2\sqrt{2}$

44284.The trapezoid shown in the given figure represents a cross section of the rudder of a ship.If the distance from A to B is 13 feet, what is the area of the cross section of the rudder in square feet?
39
40
41
42
Explanation:

The formula for calculating the area of a trapezoid is

$Area=\dfrac{1}{2}\left(base1+base2\right)\left(height\right)$

The bases of the trapezoid are given as 2 feet and 5 feet, so only the height (AQ) needs to be found.

Since the dashed line AB=13 feet, and triangle BQA is a right triangle, use the Pythagorean theorem to calculate AQ.Thus,

AQ=$\sqrt{13^{2}-5^{2}}$

=$\sqrt{144}$

=12

Substituting the values into the formula for calculatingthe area of a trapezoid:

$Area=\dfrac{1}{2}\left(2+5\right)\left(12\right)$

=42 square feet

44285.If O is the center of the circle above, what fraction of the circular region is shaded?
$\dfrac{1}{12}$
$\dfrac{1}{9}$
$\dfrac{1}{6}$
$\dfrac{1}{3}$
Explanation:

Vertical angles are congruent, so $150^{o}+150^{o}=300^{o}$ of the circle is not shaded.

Since there are $360^{o} $in a circle, this makes

$360^{o}−300^{o}=60^{o}$ of the circle shaded.

The fraction of the circular region that is shaded is thus

=$\dfrac{60}{360}$

=$\dfrac{1}{6}$

44295.A rectangular park 60 m long and 40 m wide has two concrete crossroads running in the middle of the park and rest of the park has been used as a lawn. If the area of the lawn is 2109 sq. m, then what is the width of the road?
1.5m
2.5m
3.5m
4.5m
Explanation:

Let the width of the road be x meters.

Then, (60 – 2x)(40 – 2x) = 2109

=> 2400 – 200x + 4$x^{2}$ = 2109

=> 4$x^{2}$ – 200x + 291 = 0

=> x = (200 ± 188) / 8 = 1.5 or 48.5

But width of road cannot be greater than breadth of the park. Thus, width of road = 1.5m.

44296.A lawn is in the shape as shown. Find the area of the lawn.
151 sq. m
152 sq. m
153 sq. m
154 sq. m
Explanation:

The lawn is in the form of a rectangle with two semicircles on opposite ends of the width.

Area of the rectangle = 200m x 14m = 2800 sq. m

Radius of the semicircles = $\dfrac{14}{2}$ m = 7 m

Area of the two semicircles = $2\times\left(\dfrac{\pi R^{2}}{2}\right)$

=$ \dfrac{22}{7} \times 7 \times 7 $

= 154 sq. m.

44297.ABCD is a square with one vertex at the center of the circle and two vertices on the circle. What is the length of the diagonal of the square if the area of the circle is 100 square cm?
$\dfrac{10}{\sqrt{\pi}}\sqrt{2}cm$
$\dfrac{20}{\sqrt{\pi}}\sqrt{2}cm$
$\dfrac{30}{\sqrt{\pi}}\sqrt{2}cm$
$\dfrac{40}{\sqrt{\pi}}\sqrt{2}cm$
Explanation:

Area of circle = $\pi R^{2}$

=100 sq. cm

$R^{2}=\dfrac{100}{\pi}$ Or, $R =\dfrac{10}{\sqrt{\pi}}cm$

From the figure, side of square, a = Radius of circle, $R = \dfrac{10}{\sqrt{\pi}}cm$

Diagonal of the square = $a{\sqrt{2}}$

$=\dfrac{10}{\sqrt{\pi}}\sqrt{2}cm$

44298.The floor plan of a house is shown below. Determine the area covered by the house.
$1005 feet^{2}$
$1006 feet^{2}$
$1007 feet^{2}$
$1008 feet^{2}$
Explanation:

Let's first divide the diagram of the house into two rectangles and a trapezoid, since we can calculate the area of each of these figures.

Now, the area of the larger rectangle=$40 feet \times 20 feet$

$=800 feet^{2}$

The area of the smaller rectangle=$25 feet \times 6 feet$

=$150 feet^{2}$

The area of the trapezoid A=$\dfrac{1}{2}h\left(b1+b2\right)$

The height (h) is 6 feet, and the two bases (b1 and b2) are 8 and 11 feet.

A=$\dfrac{1}{2}6\left(8+11\right)$

A=$\dfrac{1}{2}6\left(19\right)$

=$57feet^{2}$

Therefore Adding all three areas gives a total area of the house =800+150+57

$= 1,007 feet^{2}$

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