Aptitude - Area - Discussion
Discussion Forum : Area - General Questions (Q.No. 7)
7.
A towel, when bleached, was found to have lost 20% of its length and 10% of its breadth. The percentage of decrease in area is:
Answer: Option
Explanation:
Let original length = x and original breadth = y.
| Decrease in area |
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 Decrease % = |
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7 | xy x | 1 | x 100 |  % |
= 28%. |
| 25 | xy |
Discussion:
28 comments Page 1 of 3.
Zubair khan said:
1 decade ago
Let width=x and length=y
Area(A1)=xy
New meters after washing-
Width reduced by 20% and length by 10%
Thats why
Width= x-x*(20/100)=x*{1-(2/10)}=x*8/10
Lenght= y-y*(10/100)=y*{1-(1/10)}=y*9/10
New area(A2)= xy*72/100
Area reduced=A1-A2
=xy{1-(72/100)}
=xy*(28/100)
Now it is showing clearly area reduced is 28% ans.
Note= 2% of x means (x*2/100)
=28% of xy means(xy*28/100)
Area(A1)=xy
New meters after washing-
Width reduced by 20% and length by 10%
Thats why
Width= x-x*(20/100)=x*{1-(2/10)}=x*8/10
Lenght= y-y*(10/100)=y*{1-(1/10)}=y*9/10
New area(A2)= xy*72/100
Area reduced=A1-A2
=xy{1-(72/100)}
=xy*(28/100)
Now it is showing clearly area reduced is 28% ans.
Note= 2% of x means (x*2/100)
=28% of xy means(xy*28/100)
D.Mukul Raj said:
4 years ago
According to me, the solution is;
Suppose initial size = 120(L) x 110(B) = 13200.
and,
The towel shrunk down to 100(L) x 100(B) =10000.
so difference should be 13200-10000= 3200.
And if I divide 3200 by 13200 why am i getting the decreased area to be ( 8/33 ) ie 24.24242%.
Am I right? Please anyone clarify.
Suppose initial size = 120(L) x 110(B) = 13200.
and,
The towel shrunk down to 100(L) x 100(B) =10000.
so difference should be 13200-10000= 3200.
And if I divide 3200 by 13200 why am i getting the decreased area to be ( 8/33 ) ie 24.24242%.
Am I right? Please anyone clarify.
(2)
Niks said:
6 days ago
Let's assume l is 100 and b is 30. (b remains less than l).
So, area = l*b= 100*30=3000.
Now, 20% decrease in l is 20%of 100=20, and 10% decrease in b is 10%of 30=3
l = 100-20=80;
b = 30-3 = 27
Area= 80 * 27 = 2160.
% decrease = total-area decreased/total = 3000-2160/300*100 = 28%
So, area = l*b= 100*30=3000.
Now, 20% decrease in l is 20%of 100=20, and 10% decrease in b is 10%of 30=3
l = 100-20=80;
b = 30-3 = 27
Area= 80 * 27 = 2160.
% decrease = total-area decreased/total = 3000-2160/300*100 = 28%
Manish said:
1 decade ago
Towel is like rectangle, so area of rectangle is (l*b).
Let l=100, and b =50, so area =l*b =1500.
In question 20% decrease in length and and 10% decrease in breadth.
So new length is 80 and new breadth is 45, so new area =80*45 = 3600.
% decrease in area is (A1-A2) /A1*100 = 28%.
Let l=100, and b =50, so area =l*b =1500.
In question 20% decrease in length and and 10% decrease in breadth.
So new length is 80 and new breadth is 45, so new area =80*45 = 3600.
% decrease in area is (A1-A2) /A1*100 = 28%.
Ajay said:
1 decade ago
Let the original length be 20, and breadth = 10.
Therefore original area = 200.
After decrease,
20 reduced to 16 (20% reduction in length).
10 reduced to 9 (10% reduction in breadth).
Therefore 16 x 9 = 144.
200 - 144 = 56.
56/200 = 0.28 i.e. 28%.
Therefore original area = 200.
After decrease,
20 reduced to 16 (20% reduction in length).
10 reduced to 9 (10% reduction in breadth).
Therefore 16 x 9 = 144.
200 - 144 = 56.
56/200 = 0.28 i.e. 28%.
Sabir said:
1 decade ago
Nanii ..
Let the original length be 100cm n d breadth be also 100 cm
the lengths n breadths after washing will be 80 and 90 ..
Original area= 100*100 = 10000 cm2
New Area= 80*90 = 7200 cm2
So percentage decrease = (10000-7200)/100 = 2800/100 = 28%
:)
Let the original length be 100cm n d breadth be also 100 cm
the lengths n breadths after washing will be 80 and 90 ..
Original area= 100*100 = 10000 cm2
New Area= 80*90 = 7200 cm2
So percentage decrease = (10000-7200)/100 = 2800/100 = 28%
:)
Sreelu said:
9 years ago
There is another simple method.
Let's assume L = 10 and B = 10.
Then area will be 100 (L * B).
When L lost 20% it gets the value 8.
Like that, B lost 10% it gets the value of 9.
So, the new area is 72 i.e (8 * 9).
Then % decrease = 100 - 72 = 28.
Let's assume L = 10 and B = 10.
Then area will be 100 (L * B).
When L lost 20% it gets the value 8.
Like that, B lost 10% it gets the value of 9.
So, the new area is 72 i.e (8 * 9).
Then % decrease = 100 - 72 = 28.
(1)
Kpkakadiya said:
3 years ago
Let L=10, B=10.
area = 10 * 10 = 100.
Now after bleached,
L = 80% of L
= 80% of 10,
= 8.
B= 90% of B,
= 90% of 10.
= 9.
Area = 8*9 = 72.
Decrease of area in % = (100 - 72 * 100)/100.
= 28.
area = 10 * 10 = 100.
Now after bleached,
L = 80% of L
= 80% of 10,
= 8.
B= 90% of B,
= 90% of 10.
= 9.
Area = 8*9 = 72.
Decrease of area in % = (100 - 72 * 100)/100.
= 28.
(4)
Pinku said:
6 years ago
x=a*80/100
y=b*90/100
Area=x*y=80*a*90*b/100*100=72/100(a*b)
decreased area=total area(ab)-72ab/100
=ab-72ab/100
=100-72(ab/100)
=28/100(ab)
= 0 .28ab or 28ab%.
Decreased area by 28%.
y=b*90/100
Area=x*y=80*a*90*b/100*100=72/100(a*b)
decreased area=total area(ab)-72ab/100
=ab-72ab/100
=100-72(ab/100)
=28/100(ab)
= 0 .28ab or 28ab%.
Decreased area by 28%.
Kunal said:
1 decade ago
It can also solve by percentage rule.
Suppose a towel area is 100 decreases by 20% and then 10%.
The are of towel= 100 of 20%=20 (say a).
Then, 80 of 10%=8 (say b).
Towels area=a+b.
20+8 = 28% answer.
Suppose a towel area is 100 decreases by 20% and then 10%.
The are of towel= 100 of 20%=20 (say a).
Then, 80 of 10%=8 (say b).
Towels area=a+b.
20+8 = 28% answer.
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