SHORT METHODS. Multiplication and Division. Art. 1. To multiply a number by 50: Multiply } of the number by 100. Why? 46 x 50 of 46 x 100 = 2300 Multiply: 46 by 50 52 by 50 53 by 50 (a) Find the sum of the fifteen products. Art. 2. To multiply a number by 51: Take 50 times the number, to which add the number itself. Why? 48 x 50 50 times 48 = 2400 2400 + 48 = 2448 37 x 51 50 times 37 = 1850 1850 + 37 = 1887 Multiply: 36 by 51 38 by 51 39 by 51 (b) Find the sum of the fifteen products. Art. 3. To multiply a number by 52: Take 50 times the number, to which add twice the number. Why? 34 x 52 50 times 34 = 1700 1700 + 68 = 1768 45 x 52 50 times 45 = 2250 2250 + 90 = 2340 Multiply: 36 by 52 44 by 52 23 by 52 (c) Find the sum of the twelve products. Art. 4. To multiply a number by 49: Take 50 times the number, from which subtract the number itself. Why? 24 x 49 50 times 24 = 1200 1200 24 = 1176 33 x 49 50 times 33 = 1650 1650 33 = 1617 Multiply: 16 by 49 46 by 49 43 by 49 (d) Find the sum of the nine products. Art. 5. To multiply a number by 33}: Multiply ý of the number by 100. Why? 36 x 33} of 36 x 100 = 1200 Multiply: 28 by 33 22 by 33} 30 by 33 33 by 33; 35 by 333 (e) Find the sum of the nine products. Art. 6. To multiply a number by 343: Take 334 times the number, to which add the number itself. Why? 24 x 343 33į times 24 = 800 800 + 24 = 824 25 x 34 33} times 25 = 833; 833} + 25 = 8583 Multiply: 24 by 34, 39 by 341 15 by 34 17 by 34} (f) Find the sum of the twelve products. Art. 7. To multiply a number by 354: Take 33times the number, to which add twice the number. Why? 24 x 35; 333 times 24 = 800 800 + 48 = 848 25 x 35} 33} times 25 = 833} 833} + 50 = 883} Multiply: 27 by 35} 36 by 35} 33 by 35} 39 by 35 31 by 35} (g) Find the sum of the nine products. Art. 8. To multiply a number by 324: Take 33f times the number, from which subtract the number itself. Why? 21 x 32} 33} times 21 = 700 700 - 21 = 679 22 x 32 334 times 22 = 733} 733} – 22 = 7114 Multiply: 27 by 32} 36 by 32} (h) Find the sum of the nine products. = Art. 9. To multiply a number by 25: Multiply of the number by 100. Why? 48 x 25 1 of 48 x 100 = 1200 Multiply: 52 by 25 48 by 25 50 by 25 (i) Find the sum of the twelve products. Art. 10. To multiply a number by 26: number by 26: Take 25 times the number, to which add the number itself. Why? 36 x 26 25 times 36 = 900 900 + 36 = 936 Multiply: 44 by 26 32 by 26 35 by 26 (j) Find the sum of the nine products. = 900 Art. 11. To multiply a number by 27: Take 25 times the number, to which add twice the number. Why? 36 x 27 25 times 36 900 + 72 = 972 Multiply: 28 by 27 24 by 27 26 by 27 (k) Find the sum of the nine products. = 768 Art. 12. To multiply a number by 24: Take 25 times the number, from which subtract the number itself. Why? 32 x 24 25 times 32 800 800 32 Multiply: 48 by 24 52 by 24 54 by 24 (1) Find the sum of the twelve products. Art. 13. To multiply a number by 20: Multiply } of the number by 100. How may a number be multiplied by 21? By 22? By 19 ? 35 x 21 20 times 35 = 700 700 + 35 = 735 Multiply: 36 by 19 (m) Find the sum of the nine products. Art. 14. To multiply a number by 163: Multiply á of the number by 100. How may a number be multiplied by 17z? By 18z? By 15ş? 24 x 17 163 times 24 = 400 400 + 24 Multiply: 30 by 18; 30 by 15 36 by 17% 36 by 18 36 by 15 (n) Find the sum of the nine products. = 424 |