(Q1)Due to a decrease in price per kg. of sugar by 25% by how much percent, a housewife should increase quantity so that total expenditure remains same.

Solution: Let initial price=Rs. 100

Now,

% Increase=(25/75)×100

=33.33% Ans

Rough: New price=100×(100-25)/100

=Rs75

Concept:[जब Question  में कहा जाए कि Total Expenditure same है तो आपलोगों को Quantity always price का reverse लेना है.

Explanation:[पहले housewife Rs 100 में 75 kg sugar खरीदती थी जब price decrease किया तो Rs 75में  100kg sugar खरीदती है तो इस तरह से housewife 25 kg अधिक sugar खरीद पा  रही है ]

BY TRICK:

% increase=(25/100−25)×100

=(25/75)×100

=33.33% Ans.

(Q2)Due to increase in price per kg of sugar by 25% by how much percent, a housewife should decrease quantity so that total expenditure remains same.

Solution: Let initial price=Rs100

Now,

%decrease= (25/125)×100

=20% Ans

Rough: New price=100×(100+25)/100

=Rs125

BY TRICK:

%Decrease=(25/100+25)×100

=(25/125)×100

=20% Ans.

(Q3)If the price of sugar rises from Rs 6 per kg to Rs 7.50 per kg, a person to have no increase in his expenditure on sugar, will have to reduce his consumption of sugar by:

Solution:

% Reduce=(1.50/7.50)×100

=20% Ans

(Q4)The length of the rectangle is increased by 60%.By what percent would the breadth be decreased to maintain the same area?

Solution: Area of rectangle=Length ×Breadth

Let initial length=100

% Decrease=(60/160)×100

=37½% Ans.

Concept: Breadth, Length का reverse लिया गया है because Area is same.

BY TRICK:

% Decrease=(60/100+60)×100

=(60/160)×100

=37½% Ans.

(Q5)One side of a square is increased by 30%.To maintain the same area, the other side will have to be decreased by.

Solution: Area of square=Side×Side

Let initial length of side=100

Now,

% Decrease=(30/130)×100

=23¹/3% Ans.

BY TRICK:

% Decrease=(30/100+30)×100

=23¹/3% Ans.

(Q6)The height of a triangle is increased by 10% to retain the original area of the triangle,its corresponding base must be decreased by:

Solution: Area of Triangle=½×base×height

Let initial height=100

%Decrease=(10/110)×100

=9¹/11% Ans.

BY TRICK:

%Decrease=(10/100+10)×100

=(10/110)×100

=9¹/11% Ans