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 2 of 3.
Samuel said:
1 decade ago
It can also be solved as thus. Reduction in length = 100 - 20 = 80% which is 80/100.
Reduction in width= 100 - 10 = 90%.
Which is 90/100.
80/100* 90/100* 100 = 72.
100 - 72 = 28%.
Reduction in width= 100 - 10 = 90%.
Which is 90/100.
80/100* 90/100* 100 = 72.
100 - 72 = 28%.
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.
Vinayak Nayak said:
6 months ago
Consider L = 10 and breadth = 10
Then 20% less in length = 8 and 10% in breadth = 9.
now area = l * b= 8 * 9 = 72,
total area = 100,
new area = 100-72=28.
Then 20% less in length = 8 and 10% in breadth = 9.
now area = l * b= 8 * 9 = 72,
total area = 100,
new area = 100-72=28.
(1)
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.
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.
Harsha said:
1 decade ago
A1 = 100*100 = 10000 (ORIGINAL AREA).
A2 = 80*90 = 7200 (DECREASED IN AREA).
A2-A1 = 2800.
(A2-A1)% = 28%.
A2 = 80*90 = 7200 (DECREASED IN AREA).
A2-A1 = 2800.
(A2-A1)% = 28%.
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?
Sriram said:
1 decade ago
So simple by a formula.
x% decrease in length y% decrease in breadth then area change is -x-y+(x*y)/100.
x% decrease in length y% decrease in breadth then area change is -x-y+(x*y)/100.
(1)
OMARFARUK said:
5 years ago
Main formula +-p+-q+-(pq/100).
-20-10+(20* 10 / 100) = -28%.
(-ve) indicates area decrease.
-20-10+(20* 10 / 100) = -28%.
(-ve) indicates area decrease.
Deepak virat said:
5 years ago
80*90/100 = 72.
As we see 28 is reduced so we can say that the percentage decrease is 28%.
As we see 28 is reduced so we can say that the percentage decrease is 28%.
(1)
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