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.
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.
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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).
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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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