Aptitude - Area - Discussion

Why all of them taking a length as 100 that and is not a square. Why don't you try it length and breadth with separate values like 100 & 200?

What if you don't know what the percentage of increase or decrease is and what if one side is increasing and the other is decreasing?

Let a = percentage change(increase or decrease)on one side and b= percentage change of other side then:
If both sides as are increasing = (a + b) + ab/100.
If both sides are decreasing = (a + b) - ab/100.
If one side is increasing (positive, say a) and one side is decreasing (negative, say b) = a - b - ab/100.

Trick:
If increase in length of breadth & width is x% then the increase in area a' = 2x + (square x)/100.

Quick method: if x=20% then a'.

20 * 2 + (20 * 20 = 4.00) = 44.00.

If x = 4 then a' = 4 * 2 + 0.(4 * 4) = 8 + 0.16 = 8.16%
If x = 5 then a' = 5 * 2 + 0.(5 * 5) = 10 + 0.25 = 10.25.
If x = 6 then a' = 6 * 2 + 0.(6 * 6) = 12 + 0.36 = 12.36.
If x = 7 then a' = 7 * 2 + 0.(7 * 7) = 14 + 0.49 = 14.49.
If x = 8 then a' = 8 * 2 + 0.(8 * 8) = 16 + 0.64 = 16.64.
If x = 9 then a' = 9 * 2 + 0.(9 * 9) = 18 + 0.81 = 18.81.
If x = 10 then a' = 10 * 2 + 0.(10 * 10) = 20 + 1.00 = 21.
If x = 11 then a' = 11 * 2 + 0.(11 * 11) = 22 + 1.21 = 23.21.

Note : When the product is a number of more than three decimals, place a decimal point after two places from the right.

The rational number with recurring decimal expansion 0.12 is __________.

Can anyone answer the question?

If let it 100. It will make more easy.

@Bhupendra.

How did you get the new side as 6x/5?

Increased percentage is 20%.
that means 120%.
For both sides, 120/100 * 120/100 = 144/100.
i.e 44% more than 100.

Explained well @Shashank.

Shortcut :

20 + 20 + ((20 * 20)/100) = 44.

Let each side 100.
Area 100 * 100,
Increased area 120 * 120,
(14400-10000) ÷ 10000 = .44,
0.44 * 100 = 44%.