Percentage-% Change YouTube Lecture Handouts for Himachal Pradesh PSC

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Percent Change Problems (Aptitude): 15 Sec Shortcut Tricks (Marks, Population, Area)

Percentage- % Change

Types of percent problems

Types of Percent Problems

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If the Sides of Cube is Increased by 100%. Find the % Change in Its Area. What About Volume?



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There are 3 cubes whose size increased by 200% 1st cube to 2nd cube and increased by 300% 1st cube to 3rd cube that is change in the side of the cube and substitute problem would ask me what would be corresponding percent change in the area, surface area of the cube and volume of the cube.


Side of the cube increased by 100%

Surface area of cube

If the Base Radius of a Right Circular Cylinder is Increased by 15%, and Its Height is Reduced by 20%, Find the Percentage Change in Its Volume

Formula of a right circular cylinder

Radius because increased by 15%

Its height is reduced by 20%

You can and would be canceling out.

Remember that % change is always with respect to the original quantity if nothing else is specified the problem.

Krishna’s Salary is 20 % Less Than Radha. By What % is Radha’s Salary More Than Krishana?

There are two person Krishna and Radha.

Radha salary

Krishna’s salary is 20 % less than Radha so, Krishna salary

Which Would Produce Greater Net Income on Gross of 2000? 10% Tax over 200 Rs 12% Tax over 400 Rs

10% tax over 200

12% tax over 400


A Labour Works 60 Hr. Per Week and He Earns Rs. 2400. If His Per Hour Salary is Increased by 16 % and Hours Reduced by 20%. Find the % Change in His Income

Let assume is salary (increased 16%)

(Reduce 20%)


% Change

Original value

If the Numerator of a Fraction is Increased by 200% and the Denominator is Increased by 360%, the Resultant Fraction is 5/12. What Was the Original Fraction?

Let’s assume the fraction would be

If the Income Tax Were to be Increased by 19% then Net Income is Reduced by 1%. Find the Current Rate of Income Tax

100% increase in tax reduction income

19% increase in tax 1% income

Tax and Income

Gross income

Calculate the tax: gross income is made up of I and 19T

The Population of a Village is 9600. If the Males and Females Are Increased by 8% and 5%, then Population Will Become 10,272 After 1 Year. Find the Number of Males at Present

Total population of a village

We assume 100m (Male) and 100f (Female) 

Relative increase and decrease

Relative Increase and Decrease

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Increased by 5%


Difference of male:

In a Town, the Population Was 8000. In One Year, Male Population Increased by 10% and Female Population Increased by 8% but the Total Population Increased by 9%. The Number of Males in the Town Was?


Assume that 100m and 100f

Increase everything by

Male and female

The total population increased by 9%:


Therefore, the number of 40 males in the town.

When a Student Scores 30% Marks then He Fails by 5 Marks. However, when He Score 40% Marks then He Gets 10 More Than Passing Marks. Find Maximum Marks. What About Passing %?

Here, there are two scale: relative scale and absolute mark

Relative and absolute scale

Relative and Absolute

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Total mark

Passing mark


Next Class- % Expenditure, Commission, Salary, & Bonus