Aptitude - Area - Discussion

Let orginal area of rectangle is 1,
Given; L=1/2(halved) and b= 3 (tripled)
now new area= 1/2 * 3.
= 1.5.
Hence, the new area increased by 1.5-1=0.5.
So, the percentage increased by 0.5/1*100=50%.

Assume that rectangle is 100.
Decreased by halved i.e = 50.
Increased by tripled means = 300.
So, % change is = (50 * 300)/100.
= 150.
i.e 50% more than 100.
So 50% increases.

It is simple:

(L*1/2)(B*3),
LB*(3/2),
LB*(1.5).

So clearly, 50% increased.

Let, length = 100 and breadth = 100.

New area:Previous area = {(100/2)*(100*3)}:{100*100}.

= 150:100.

So increase = 50%.

Please explain me how the last step came.

Say, length to be x and breadth to be y.

After modification: Length becomes x/2 and breadth becomes 3y.

Previous Area, A' = xy and the New Area, A = {3/2*(xy)}.

Difference in Area, A-A' = 3/2 = 1.5 hence 50% increase.

Its very simple:

Consider length and breadth to be 100.

So area should be 100 X 100 = 10,000 sq unit.

But according to given condition if length is halved then it becomes 50 (100/2) and breadth is tripled it becomes 300(100X3) So new area is 50 x 300= 1500 sq unit.

It is greater than the area if length and breadth were not altered. Therefore increase is there,

Secondly change is area is:

{(15000-10000)/10000}x 100 = 50%.

By using this method:

-50+300+((-50)(300)/100),
100%.

First of all, we all know that the area of rectangle is l*b so area(old) =lb, now according to the question it is length is halved so it is l/2 and the breadth is increased by 3times so it is 3b so by area formula it product of l and b =new area=(l/2)*(3b) =3/2(lb),so in order to find the difference we have subtract the new area from the old area so new area-old area =lb/2.

So in order to convert it to percentage multiply by 100i.e (lb)/2*(100) = 50 percent.

Why x + y + xy/100 not taken?