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.
Santho said:
1 decade ago
x+y-(x*y/100)
Then, 20% + 10%-[20*10/100] = 28%
Then, 20% + 10%-[20*10/100] = 28%
Nani said:
1 decade ago
Please explain clearly anyone of you.
XYZ said:
1 decade ago
SANTHO your explanation short and sweet. But why we use x+y in all problems your formula will work or not?
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%
:)
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%.
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)
Abc said:
1 decade ago
x+y-(x*y/100)------------when area is decreasing
x+y+(x*y/100)---------------when area is increasing,all this type of prblms.
x+y+(x*y/100)---------------when area is increasing,all this type of prblms.
Manoranjan said:
1 decade ago
Hi.
Take L=100 nd B=100.
Then 20% in L and 10% in B.
Then new L and B are 80 and 90.
Area=100*100=10000.
New area =7200 then 10000-7200=2800.
Now 2800/10000*100=28 answer.
Take L=100 nd B=100.
Then 20% in L and 10% in B.
Then new L and B are 80 and 90.
Area=100*100=10000.
New area =7200 then 10000-7200=2800.
Now 2800/10000*100=28 answer.
Rahul said:
1 decade ago
If Area, A=XY
the d(A)/A= dX/X + dY/Y
=10+20
=30%
Whats wrong with this method of differentiation?
because answer is not matching.
the d(A)/A= dX/X + dY/Y
=10+20
=30%
Whats wrong with this method of differentiation?
because answer is not matching.
Sania said:
1 decade ago
But shouldn't the area of a towel be (l+b).
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