32
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%

Explanation:

New radius = $\inline \fn_cm \frac{50}{100}R$$\inline \fn_cm \frac{R}{2}$

Original area =$\inline \fn_cm \tiny \prod R^{2}$  and new area = $\inline \fn_cm \tiny \prod(\frac{R}{2})^{2}=\frac{\prod R^{2}}{4}$

Decrease in area = $\inline \fn_cm \tiny \frac{3\prod R^{2}}{4}\times \frac{1}{\prod R^{2}}\times 100$ = 75%

Q:

If a 36 cm thread is used to wrap a book, lengthwise twice and breadth wise once, what is the size of the book ?

 A) 288 sq.cm B) 188 sq.cm C) 144 sq.cm D) 244 sq.cm

Explanation:

Length of the thread is 36 cms.
length wise twice breath wise once then totally thrice.
so 36/3 = 12.
so length is 12 x 2 = 24 cms
breath is 12 cms
Area of the book = length x breath = 24 x 12 = 288 sq.cm

2 36
Q:

If 4 circles of equal radius are drawn with vertices of a square as the centre , the side of the square being 7 cm, find the area of the circles outside the square ?

 A) 119.21 sq cm B) 115.395 sq cm C) 104.214 sq cm D) 111.241 sq cm

Explanation:

Because each vertice of the square is the center of a circle
(1/4) part of the total area of each circle inside of the square.
(3/4) part of the total area of each circle outside of the square.
Thus total area outside the square is $\inline \fn_jvn \small 4\left ( \frac{3}{4}x\prod x3.5x3.5 \right )$ = 115.3955 sq cm.

2 42
Q:

What is the least number of squares tiles required to pave the floor of a room 15 m 17 cm long and 9 m 2 cm broad ?

 A) 844 B) 814 C) 840 D) 820

Explanation:

Length of largest tile = H.C.F. of 1517 cm and 902 cm = 41 cm.
Area of each tile = (41 x 41) sq.cm

Required number of tiles =1517 x 902/(41 x 41) = 814.

4 141
Q:

A rectangular grassy plot 120 m. by 60 m has a gravel path 1.5 m wide all round it on the inside. Find the cost of gravelling the path at 65 paise per sq. metre ?

 A) Rs. 345.15 B) Rs. 245.1 C) Rs. 234.18 D) Rs. 456.65

Explanation:

area of the plot = 120m x 60m = 7200 sq.m
area of plot excluding gravel = 117m x 57m = 6669 sq.m
area of gravel = 7200 sq.m - 6669 sq.m = 531 sq.m
cost of building it = 531 sq.m x 65 ps
= 34515 ps
In Rs. = 34515/100 = Rs. 345.15.

Filed Under: Area - Quantitative Aptitude - Arithmetic Ability
Exam Prep: Bank Exams , CAT
Job Role: Bank PO

4 48
Q:

The area of a square is 1024 sq.cm. What is the ratio of the length to the breadth of a rectangle whose length is twice the side of the square and breadth is 12 cm less than the side of this square ?

 A) 14:9 B) 13:12 C) 16:5 D) 17:13