Question

On increasing the length of a rectangle by 20% and decreasing its breadth by 20%, what is the change in its area?

पर्याय

• 20% increase

• 20% decrease

• No change

• 4% decrease

Answer 1

4% decrease

Explanation:

Let the length be `l` m and breadth be b m.

Then, original area = (`l` × b) m² = `l`b m².

New length = `(l xx 120/100) m = (6l)/5 m`,

New breadth = `(b xx 80/100) m = (4b)/5 m`.

New area = `((24lb)/25) m^2`.

Change in area = `(lb - (24lb)/25) m^2 = (lb)/25 m^2`.

∴ % change = `(lb xx 100)/(25 xx lb) % = 4%`.