Simplification and approximation are crucial topics in quantitative aptitude, commonly tested in competitive exams. Mastering these formulas can help you solve problems quickly and accurately.
Commutative Property:
a + b = b + a
a - b ≠ b - a
Associative Property:
(a + b) + c = a + (b + c )
Commutative Property:
a × b = b × a
a ÷ b ≠ b ÷ a
Associative Property:
(a × b) × c = a × (b × c)
Distributive Property:
a × (b + c) = a × b + a × c
a × (b - c) = a × b - a × c
The order in which operations should be performed:
B – Brackets
O – Orders (Powers & Roots)
D – Division
M – Multiplication
A – Addition
S – Subtraction
Example:
5 + 3 × (8 ÷ 2)2
= 5 + 3 × (4)2
= 5 + 3 × 16
= 5 + 48
= 53
x% of y = (x/100) × y
y is what % of x = (y/x) × 100
Percentage Increase/Decrease:
[(New Value - Original Value)/Original Value] × 100
4. Fraction-Decimal-Percentage Conversions
Rounding Off Numbers:
If the next digit is ≥5, round up.
If the next digit is <5, round down.
Example: 4.68 ≈ 4.7 (to 1 decimal place)
Estimating Sums/Differences:
498 + 372 ≈ 500 + 370 = 870
Estimating Products:
49 × 31 ≈ 50 × 30 = 1500
Number | Cube |
---|---|
1 | 1 |
2 | 8 |
3 | 27 |
4 | 64 |
5 | 125 |
6 | 216 |
7 | 343 |
8 | 512 |
9 | 729 |
10 | 1000 |
√2 ≈ 1.414
√3 ≈ 1.732
√5 ≈ 2.236
√10 ≈ 3.162
Cube root of 2 ≈ 1.26
Cube root of 3 ≈ 1.442
(a + b)2 = a2 + 2ab + b2
(a - b)2 = a2 - 2ab + b2
a2 - b2 = (a + b)(a - b)
(a + b)3 = a3 + 3a2b + 3ab2 + b3
(a - b)3 = a3 - 3a2b + 3ab2 - b3
Number | Rule |
---|---|
2 | Last digit is even (0,2,4,6,8) |
3 | Sum of digits divisible by 3 |
4 | Last two digits divisible by 4 |
5 | Ends with 0 or 5 |
6 | Divisible by both 2 and 3 |
8 | Last three digits divisible by 8 |
9 | Sum of digits divisible by 9 |
10 | Ends with 0 |
11 | Difference (sum of odd & even digits) divisible by 11 |
Practice mental math for faster calculations.
Use approximation when exact computation is time-consuming.
Memorize key squares, cubes, and roots for quick solving.
This guide covers essential formulas to tackle simplification and approximation problems efficiently. Keep practicing to improve speed and accuracy!
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