Mathematics

Important points

1. 1

   x% of y is the same as y% of x.

2. 2

   Profit % = (Profit ÷ Cost Price) × 100.

3. 3

   Two successive discounts of a% and b% equal a single discount of (a + b − ab/100)%.

4. 4

   Simple Interest = P × R × T / 100; Compound amount = P(1 + R/100)ᵀ.

5. 5

   To convert km/h into m/s, multiply by 5/18.

6. 6

   Average speed for equal distances at speeds x and y = 2xy / (x + y).

7. 7

   Product of two numbers = HCF × LCM.

8. 8

   A number is divisible by 3 if the sum of its digits is divisible by 3.

9. 9

   Area of a circle = πr²; circumference = 2πr.

10. 10

    Sum of interior angles of an n-sided polygon = (n − 2) × 180°.

11. 11

    sin²θ + cos²θ = 1.

12. 12

    Pythagoras theorem: a² + b² = c² in a right-angled triangle.

Topic-wise notes

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