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Q:

If the radius of a circle is decreased by 50%, find the percentage decrease in its area.

A) 55%	B) 65%
C) 75%	D) 85%

Answer & Explanation Answer: C) 75%

Explanation:

Let original radius = R.

New radius = $\frac{50}{100} R$ = $\frac{50}{100} R$

Original area = $\frac{R}{2}$ and new area = ${πR}^{2}$

$\frac{3 {πR}^{2}}{4} * \frac{1}{{πR}^{2}} * 100$

Decrease in area = $π {(\frac{R}{2})}^{2} = \frac{{πR}^{2}}{4}$ = 75%

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Filed Under: Area
Exam Prep: Bank Exams
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Q:

If the length of a certain rectangle is decreased by 4 cm and the width is increased by 3 cm, a square with the same area as the original rectangle would result. Find the perimeter of the original rectangle.

A) 20	B) 30
C) 40	D) 50

Answer & Explanation Answer: D) 50

Explanation:

Let x and y be the length and breadth of the rectangle respectively.
Then, x - 4 = y + 3 or x - y = 7 ----(i)
Area of the rectangle =xy; Area of the square = (x - 4) (y + 3)
(x - 4) (y + 3) =xy <=> 3x - 4y = 12 ----(ii)
Solving (i) and (ii), we get x = 16 and y = 9.
Perimeter of the rectangle = 2 (x + y) = [2 (16 + 9)] cm = 50 cm.

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Filed Under: Area
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Q:

If each side of a square is increased by 25%, find the percentage change in its area.

A) 56.25%	B) 36.25%
C) 16.25%	D) 12.25%

Answer & Explanation Answer: A) 56.25%

Explanation:

Let each side of the square be a. Then, area = . $a^{2}$
New side = $\frac{125 a}{100} = \frac{5 a}{4}$ . New area = ${(\frac{5 a}{4})}^{2}$ = $(\frac{25 a^{2}}{16})$

Increase in area = $\frac{25 a^{2}}{16} - a^{2} = \frac{9 a^{2}}{16}$
Increase% = $[\frac{9 a^{2}}{16} * \frac{1}{a^{2}} * 100]$ % = 56.25%.

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Filed Under: Area
Exam Prep: Bank Exams
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Q:

A man walked diagonally across a square lot. Approximately, what was the percent saved by not walking along the edges?

A) 30	B) 40
C) 50	D) 60

Answer & Explanation Answer: A) 30

Explanation:

Let the side of the square(ABCD) be x meters.

Then, AB + BC = 2x metres.

AC = $\sqrt{2 x}$ = (1.41x) m.

Saving on 2x metres = (0.59x) m.

Saving % = $\frac{0.59 x}{2 x} * 100$ = 30% (approx)

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Q:

The percentage increase in the area of a rectangle, if each of its sides is increased by 20%

A) 22%	B) 33%
C) 44%	D) 55%

Answer & Explanation Answer: C) 44%

Explanation:

Let original length = x metres and original breadth = y metres.

Original area = xy sq.m

Increased length = $\frac{120}{100}$ and Increased breadth = $\frac{120}{100}$

New area = $\frac{120}{100} x * \frac{120}{100} y = \frac{36}{25} x y m^{2}$

The difference between the Original area and New area is:

$\frac{36}{25} x y - x y$

$\frac{11}{25} x y$ Increase % = $(\frac{\frac{11}{25} x y}{x y}) * 100$ = 44%

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Q:

There are 7 non-collinear points. How many triangles can be drawn by joining these points?

A) 10	B) 30
C) 35	D) 60

Answer & Explanation Answer: C) 35

Explanation:

A triangle is formed by joining any three non-collinear points in pairs.

There are 7 non-collinear points

The number of triangles formed = $7 C_{3}$ = 35

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Filed Under: Permutations and Combinations

Q:

Find the total number of distinct vehicle numbers that can be formed using two letters followed by two numbers. Letters need to be distinct

A) 65000	B) 64000
C) 72000	D) 36000

Answer & Explanation Answer: A) 65000

Explanation:

Out of 26 alphabets two distinct letters can be chosen in $26 P_{2}$ ways. Coming to numbers part, there are 10 ways.(any number from 0 to 9 can be chosen) to choose the first digit and similarly another 10ways to choose the second digit. Hence there are totally 10X10 = 100 ways.

Combined with letters there are $6 P_{2}$ X 100 ways = 65000 ways to choose vehicle numbers.

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Q:

Payments of $2000 and $1000 were originally scheduled to be paid one year and five years, respectively, from today. They are to be replaced by a $1500 payment due four years from today, and another payment due two years from today. The replacement stream must be economically equivalent to the scheduled stream. What is the unknown payment, if money can earn 7% compounded semiannually?

A) 1548	B) 1348
C) 1648	D) 1748

Answer & Explanation Answer: C) 1648

Explanation:

FV1 = Future value of $2000, 1 year later
= PV (1+ i)^n

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Filed Under: Compound Interest
Exam Prep: Bank Exams
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