NUMBER SYSTEM SHORTSCUTS
1. Method to multiply 2-digit number. (i) AB × CD = AC / AD + BC / BD 35 × 47 = 12 / 21 + 20 / 35 = 12 / 41 / 35 = 1645 (ii) AB × AC = A2 / A (B + C) / BC 74 × 76 = 72 / 7(4 + 6) / 4 × 6 = 49 / 70 / 24 = 49 / 70 / 24 = 5624 (iii) AB × CC = AC / (A + B)C / BC = 35 × 44 = 3 × 4 / (3 + 5) × 4 / 5 × 4 = 12 / 32 / 20 = 12 / 32 / 20 = 1540 2. Method to multiply 3-digit no. ABC × DEF = AD / AE + BD / AF + BE + CD / BF + CE / CF 456 × 234 = 4 × 2 / 4 × 3 + 5 × 2 / 4 × 4 + 5 × 3 + 6 × 2 / 5 × 4 + 6 × 3 / 6 × 4 = 8 / 12 + 10 / 16 + 15 + 12 / 20 + 18 / 24 = 8 / 22 /43 / 38 / 24 = 106704 3. If in a series all number contains repeating 7. To find their sum, we start from the left multiply 7 by 1, 2, 3, 4, 5 & 6. Look at the example below. 777777 + 77777 + 7777 + 777 + 77 + 7 = ? = 7 × 1 / 7 × 2 / 7 × 3 / 7 × 4 / 7 × 5 / 7 × 6 = 7 / 14 / 21 / 28 / 35 / 42 = 864192 4. 0.5555 + 0.555 + 0.55 + 0.5 = ? To find the sum of those number in which one number is repeated after decimal, then first write t...