# Faster Percentage Calculation

## Faster Percentage Calculation

The quickest way to calculate percentages is to multiply numbers first and handle two decimal places later.

For example, 20% of 70 is 20 x 70 = 1400, so the answer is 14.

70% of 20 is also 14.

To calculate the percentage of 72 or 29, then round up and down to the nearest multiple (70 and 30 respectively) to get a quick approx result.  Time and Work Problems - Shortcut Tricks and Formulas

Problems Type 1: .

A can finish work in X days. .

B can finish work in Y days.

Both can finish in Z days = (X*Y) / (X+Y). .

Problems Type 2: .

Both A and B together can do work in T days.

A can do this work in X days.

then, B can do it in Y days = (X*T) / (X-T) .

Problems Type 3: .

A can finish work in X days.

B can finish work in Y days.

C can finish work in Z days.

Together they can do work in T days = (X*Y*Z)/ [(X*Y)+(Y*Z)+(X*Z)] .

Problems Type 4: .

A can finish work in X days.

B can finish work in Y days.

A*X = B*Y.

...

Average calculation

N = the number of terms  .

S = the sum of the numbers in the set.

Average = S/N .

For example.

The marks of a student in five subjects are 96, 94, 92, 87, and 81, then what is the average score of the student?.

N = 5.

S = 96 + 94 + 92 + 87 + 81 = 450.

A = 450/5 = 90.

Another type questions .

1). There are 36 boys and 44 girls in a class. The average score of boys is 40 and girls are 35. Then what will be the average mark? .

Total mark of 36 boys = 36 x 40 = 1440.

Total mark of 44 girls = 35 x 44 = 1540.

Total mark of 80 Students = 1440 + 1540 = 2980 .

Average mark of the class = (2980 / 80).

...

BODMAS Rule

BODMAS is an acronym and it stands for Bracket, Of, Division, Multiplication, Addition and Subtraction. .

This explains the order of operations to solve an expression. According to Bodmas rule, if an expression contains brackets ((), {}, []) we have to first solve/simplify the bracket followed by of (powers and roots etc.), then division , multiplication , addition and subtraction from left to right. .

Example :.

7 + (6 × 52 + 3) =   7 + (6 × 25 + 3).

7 + (150 + 3).

7 + (153).

7 + 153 .

Ans: 160. .

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