Skillry

 Number System A rational number is a number that can be expressed in the form of p/q where p & q are integers and q≠0. A prime number is a number that has exactly two factors which are 1 and itself. 1.i) How to find if a number is prime or not? N is a prime number if it is not divisible by numbers lesser than √N. Example: 191 is a prime number since it is not divisible by 2, 3, 5, 7, 11, and 13 [numbers less than √191 (≈14)]. Note: Prime numbers will always be in the form (6k±1) where k= 1, 2, 3….But not all (6k±1) will be a prime number Conversion of a decimal number to fraction: Example: 6.424242……… Let    x  = 6.424242….       100x  = 642.424242…..       (100x – x)= (642.424242…. – 6.424242…..)        99x    = 636         x     = 636/99 ∴ 6.424242…… = 636/99   Divisibility Rules A number is divisible by 2 If the last digit is even. A number is divisible by 3 If the sum of the digits is divisible by 3. A number is divisible by 4 If the last two digits of the number divisible by