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SHORT METHODS

IN

MULTIPLICATION AND

DIVISION. Art. 1. To multiply a number by 50: Multiply s of the

number by 100. Why?

[blocks in formation]

Multiply:
44 by 50 32 by 50 35 by 50
36 by 50 38 by 50 27 by 50
64 by 50 42 by 50 55 by 50

82 by 50 76 by 50 43 by 50
(a) Find the sum of the twelve products.

Art. 2. To multiply a number by 51: Take 50 times the number, to which add the number itself. Why?

50 times 48 = 2400 2400 +48 = 2448
50 times 37 = 1850 1850 + 37 = 1887

48 x 51 37 x 51

Multiply:
26 by 51 34 by 51 35 by 51
46 by 51 32 by 51 29 by 51
24 by 51 42 by 51 43 by 51

66 by 51 84 by 51 33 by 51
(b) Find the sum of the twelve 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 tinies 34 = 1700 1700 + 68 = 1768
45 x 52 50 times 45 = 2250 2250 + 90 = 2340

Multiply:
26 bv 52 38 by 52 27 by 52
18 by 52 14 by 52 17 by 52
24 by 52 32 by 52 35 by 52

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:
18 by 49 22 by 49 27 by 49
28 by 49 34 by 49 35 by 49
16 by 49 46 by 49 43 by 49

26 by 49 38 by 49 31 by 49
(d) Find the sum of the twelve products.

Art. 5. To multiply a number by 33}: Multiply of the number by 100. Why? 36 x 33}

{ of 36 x 100 1200
37 x 333 of 37 x 100 = 12333

Multiply:
24 by 33 27 by 33} 28 by 33}
18 by 33} 21 by 33} 22 by 337
30 by 33} 33 by 334 35 by 33}

15 by 33} 39 by 33 41 by 33}
(e) Find the sum of the twelve products.

Art. 6. To multiply a number by 343: Take 33} times the number, to which add the number itself. Why? 24 x 345

33} times 24 = 800 800 + 24 = 824 25 x 315 33} times 25 = 8333 833} + 25 = 8583

Multiply:
18 by 315 27 by 343 24 by 31}
21 by 315 33 by 34} 39 by 343
30 by 315 36 by 343 15 by 311

12 by 343 16 by 34} 17 by 31

(f) Find the sum of the twelve products. Art. 7. To multiply a number by 35]: Take 33} times the number, to which add twice the number. Why? 24 x 353

33} times 24 = 800 800 +48 = 848 25 x 35$

33} times 25 = 833} 823} + 50 = 8833

Multiply:
21 by 355 30 by 354 27 by 35}
18 by 35$ 66 by 355 36 by 351
33 by 35%

39 by 35} 31 by 35
15 by 355 20 by 355 42 by 353

(g) Find the sum of the twelve products. Art. 8. To multiply a number by 321: Take 33} times the number, from which subtract the number itself. Why?

33] times 21 = 700 700 – 21 = 679
334 times 22 = 733 7331-22 = 711

Multiply:
15 by 32} 21 by 32}

18 by 32 24 by 32 30 by 32

27 by 32
33 by 323

39 by 32 36 by 323
66 by 32} 19 by 32} 20 by 32
(h) Find the sum of the twelve products.

21 x 32} 22 x 323

Art. 9. To multiply a number by 25: Multiply 1 of the number by 100. Why?

48 x 25 4 of 48 x 100 = 1200
49 x 25 of 49 x 100 = 1225

Multiply:
36 by 25 32 by 25 33 by 25
40 by 25 28 by 25 29 by 25
24 by 25 16 by 25 19 by 25

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: Take 25 times the number, to which add the number itself. Why?

36 x 26 25 times 36 = 900 900 + 36 = 936
37 x 26 25 times 37 = 925 925 + 37 = 962

Multiply:
36 by 26 48 by 26 45 by 26
28 by 26 24 by 26 25 by 26
44 by 26 32 by 26 35 by 26

52 by 26 16 by 26 18 by 26
(j) Find the sum of the twelve products.

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 = 900 900 + 72 = 972
37 x 27 25 times 37 = 925 925 +74 = 999

Multiply:
48 by 27 52 by 27 37 by 27
32 by 27 16 by 27 17 by 27
28 by 27 24 by 27 26 by 27

44 by 27 56 by 27 35 by 27
(k) Find the sum of the twelve products.

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 = 768
33 x 24 25 times 33 = 825 825 - 33 = 792

Multiply:
24 by 24 16 by 24 17 by 24
44 by 24 36 by 24 37 by 24
28 by 24 32 by 24 35 by 24

48 by 24 52 by 24 51 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:
45 by 21 45 by 22 45 by 19
35 by 21 35 by 22 35 by 19
36 by 21 36 by 22 36 by 19

27 by 21 27 by 22 27 by 19
(m) Find the sum of the twelve products.

Art. 14. To multiply a number by 163: Multiply & of the number by 100. How may a number be multiplied by 173? by 187? by 15} ? 24 x 173

163 times 24 = 400 400 + 24 = 424

Multiply:
18 by 173 18 by 18} 18 by 15;
30 by 173 30 by 183 30 by 153
36 by 173 36 by 18 36 by 153
42 by 173 42 by 183 42 by 153
(n) Find the sum of the twelve products.

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