ExamVeda
Login
Home
11
The difference between the length and breadth of a rectangle is 23 m. If its perimeter is 206 m, then its area is:
Discuss
Answer & Solution
Answer: Option D
Solution:
We have: (l - b) = 23 and 2(l + b) = 206 or (l + b) = 103
Solving the two equations, we get:
l = 63 and b = 40
∴ Area = (l x b) = (63 x 40) m2 = 2520 m2
12
The length of a rectangle is halved, while its breadth is tripled. What is the percentage change in area?
Discuss
Answer & Solution
Answer: Option B
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{original}}\,{\text{length}} = x\,{\text{and}}\, \cr & {\text{Original}}\,{\text{breadth}} = y \cr & {\text{Original}}\,{\text{area}} = xy \cr & {\text{New}}\,{\text{length}} = \frac{x}{2} \cr & {\text{New}}\,{\text{breadth}} = 3y \cr & {\text{New}}\,{\text{area}} = \left( {\frac{x}{2} \times 3y} \right) = \frac{3}{2}xy \cr & \therefore {\text{Increase}}\,\% = {\frac{1}{2}xy \times \frac{1}{{xy}} \times 100} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 50\% \cr} $$
13
The length of a rectangular plot is 20 metres more than its breadth. If the cost of fencing the plot @ 26.50 per metre is Rs. 5300, what is the length of the plot in metres?
Discuss
Answer & Solution
Answer: Option E
Solution:
$$\eqalign{ & {\text{Let}}\,{\text{breadth}} = x\,{\text{metres}} \cr & {\text{Then,}}\,{\text{length}} = \,\left( {x + 20} \right)\,{\text{metres}} \cr & {\text{Perimeter}} = {\frac{{5300}}{{26.50}}} m = 200m \cr & \therefore 2\left[ {\left( {x + 20} \right) + x} \right] = 200 \cr & \Rightarrow 2x + 20 = 100 \cr & \Rightarrow 2x = 80 \cr & \Rightarrow x = 40 \cr & {\text{Hence,}}\,{\text{length}} = x + 20 = 60m \cr} $$
14
A rectangular field is to be fenced on three sides leaving a side of 20 feet uncovered. If the area of the field is 680 sq. feet, how many feet of fencing will be required?
Discuss
Answer & Solution
Answer: Option D
Solution:
We have: l = 20 ft and lb = 680 sq. ft.
So, b = 34 ft.
∴ Length of fencing = (l + 2b) = (20 + 68) ft = 88 ft.
15
A tank is 25 m long, 12 m wide and 6 m deep. The cost of plastering its walls and bottom at 75 paise per sq. m, is:
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\eqalign{ & {\text{Area}}\,{\text{to}}\,{\text{be}}\,{\text{plastered}} \cr & = \left[ {2\left( {l + b} \right) \times h} \right] + \left( {l \times b} \right) \cr & = \left\{ {\left[ {2\left( {25 + 12} \right) \times 6} \right] + \left( {25 \times 12} \right)} \right\}{m^2} \cr & = \left( {444 + 300} \right){m^2} \cr & = 744{m^2} \cr & \therefore {\text{Cost}}\,{\text{of}}\,{\text{Plastering}} \cr & = Rs.\,\left( {744 \times \frac{{75}}{{100}}} \right) \cr & = Rs.\,558 \cr} $$
16
The length of a room is 5.5 m and width is 3.75 m. Find the cost of paving the floor by slabs at the rate of Rs. 800 per square metre.
Discuss
Answer & Solution
Answer: Option D
Solution:
Area of the floor
= (5.5 × 3.75)m2
= 20.625m2
∴ Cost of paying
= Rs. (800 × 20.625)
= Rs. 16500
17
An artist has completed one-fourth of a rectangular oil painting. When he paint another 100 square centimetres of the painting, he would complete three-quarters of the painting. If the height of the oil painting is 10 cm, determine the length (in cm) of the oil panting.
Discuss
Answer & Solution
Answer: Option C
Solution:
Let the area of the whole painting be x cm2
Then,
$$\eqalign{ & \Rightarrow \frac{1}{4}x + 100 = \frac{3}{4}x \cr & \Rightarrow \frac{1}{2}x = 100 \cr & \Rightarrow x = 200 \cr} $$
∴ Area of painting = 200 cm2
And, Height = 10 cm
Length of painting :
$$\eqalign{ & = \left( {\frac{{200}}{{10}}} \right)cm \cr & = 20\,\,cm \cr} $$
18
The length of a rectangle is increased by 60%. By what percent would the width have to be decreased so as to maintain the same area ?
Discuss
Answer & Solution
Answer: Option A
Solution:
Let original length = x and original breadth = y
Then, original area = xy
New length :
$$\eqalign{ & = \frac{{160x}}{{100}} \cr & = \frac{{8x}}{5} \cr} $$
Let the new breadth = z
Then,
$$\eqalign{ & \Rightarrow \frac{{8x}}{5} \times z = xy \cr & \Rightarrow z = \frac{{5y}}{8} \cr} $$
∴ Decrease in breadth :
$$\eqalign{ & = \left( {\frac{{3y}}{8} \times \frac{1}{y} \times 100} \right)\% \cr & = 37\frac{1}{2}\% \cr} $$
19
The following squares represent the monthly income of two families
Area mcq question image
If the monthly income of family A is Rs. 40000, the monthly income of family B is ?
Discuss
Answer & Solution
Answer: Option C
Solution:
$$\frac{{{\text{Monthly income of family A}}}}{{{\text{Monthly income of family B}}}}$$       $$ = \frac{{{\text{Area of square A}}}}{{{\text{Area of square B}}}}$$
$$\eqalign{ & \Rightarrow \frac{{40000}}{x} = \frac{{{2^2}}}{{{3^2}}} \cr & \Rightarrow x = \left( {\frac{{40000 \times 9}}{4}} \right) \cr & \Rightarrow x = 90000 \cr} $$
20
What will be the length of the diagonal of that square plot whose area is equal to the area of a rectangular plot of length 45 metres and breadth 40 metres ?
Discuss
Answer & Solution
Answer: Option B
Solution:
$$\eqalign{ & {\text{Area :}} \cr & = \left( {45 \times 40} \right){m^2} \Leftrightarrow \frac{1}{2} \times {\left( {{\text{Diagonal}}} \right)^2} \cr & = 1800\,\,\,\, \Leftrightarrow \,\,\,\,{\text{Diagonal}} \cr & = 60\,\,m \cr} $$