Tutorial 4 A quick way to square numbers that end in 5 using the formula BY ONE MORE THAN THE ONE BEFORE. 752 = 5625 75 means 75 x 75. The answer is in two parts: 56 and 25. The last part is always 25. The first part is the first number, 7, multiplied by the number "one more", which is 8: so 7 x 8 = 56 Similarly 852 = 7225 because 8 x 9 = 72. Exercise 1 Tutorial 4 Try these: 1) 452 = 2) 652 = 3) 952 = 4) 352 = 5) 152 = Method for multiplying numbers where the first figures are the same and the last figures add up to 10. 32 x 38 = 1216 Both numbers here start with 3 and the last figures (2 and add up to 10. So we just multiply 3 by 4 (the next number up) to get 12 for the first part of the answer. And we multiply the last figures: 2 x 8 = 16 to get the last part of the answer. Diagrammatically: And 81 x 89 = 7209 We put 09 since we need two figures as in all the other examples. Exercise 2 Tutorial 4 Practise some: 1) 43 x 47 = 2) 24 x 26 = 3) 62 x 68 = 4) 17 x 13 = 5) 59 x 51 = 6) 77 x 73 =