MENTAL ARITHMETIC:  MULTIPLICATION

PROBLEMS

To see the answer, pass your mouse over the colored area.
To cover the answer again, click "Refresh" ("Reload").
Do the problem yourself first!

1.  a)  3 × 4 cm.  What does that mean?  4 cm + 4 cm + 4 cm.

1.  a)  What is 3 called?  The multiplier.

1.  a)  What is 4 cm called?  The multiplicand.

1.  b)  4 × 3 cm.  What does that mean?  3 cm + 3 cm + 3 cm + 3 cm.

1.  b)  Which is the multiplicand?  3 cm.

1. b)   What is 4 called?  The multiplier.

2.  a)  Five 7's are what multiplication?  5 × 7

2.  b)  Six eights are what multiplication?  6 × 8

3.  According to the order property of multiplication:

Nine 6's =  Six 9's.

4.  The order of factors.  Multiply mentally.

4.  a)  2 × 9 × 6 × 5 = 10 × 54 = 540

4.  b)  7 × 25 × 8 × 4 = 100 × 56 = 5600

4.  c)  2 × 2 × 2 × 3 × 5 × 5 × 7 = (2 × 2 × 5 × 5) × 2 × 3 × 7 =

100 × 42 = 4200

5.  When numbers are repeatedly added, we obtain their multiples.  Write
5.  the first six multiples of the following.

5.  a)   25.   25, 50, 75, 100, 125, 150.

5. b)   12.   (To go to each next multiple of 12:  12 = 10 + 2.
5.  b)   12.   Thus 24 + 12 = 24 + 10 + 2 = 34 + 2 = 36.)
5.  b)   12.   12, 24, 36, 48, 60, 72.

5.  c)   35.   35, 70, 105, 140, 175.

5.  d)   75.   75, 150, 225, 300, 375, 450.

5.  e)   18.   (To go to each next multiple of 18:  18 = 20 − 2.
5.  b)   12.   Thus 18 + 18 = 18 + 20 − 2 = 38 − 2 = 36.)
5.  b)   12.  18, 36, 54, 72, 90, 108.

6.  Whole numbers that end in 0's.  Calculate mentally.

6.  a)  3 × 60 = 180               b)  30 × 600 = 18,000

6.  c)  300 × 6000 = 1,800,000

5.  d)  9 × 50 = 450                 e)  40 × 7 = 280              f)  60 × 8 = 480

5.  g)  250 × 300 = 75,000           h)  2000 × 1200 = 2,400,000

5.  i)  700 × 700 = 490,000          j)  3,000 × 15,000 = 45,000,000

7.  Calculate mentally.

7.  a)  6 × $.40 = $2.40       b)  7 × $.30 = $2.10      c)  8 × $.60 = $4.80

6.  d)  9 × $.70 = $6.30      e)  5 × $.80 = $4.00      f)  4 × $.50  = $2.00

8.  Expanding into units.  Calculate in writing by expanding the
7.  multiplier into its tens and ones.

8.  a)  15 × 3.  (10 threes + 5 threes) = 30 + 15 = 45.

8.  b)  14 × 7 = Ten 7's + Four 7's = 70 + 28 = 98

8.  c)  17 × 9 = Ten 9's + Seven 9's = 90 + 63 = 153

8.  d)  32 × 6 = 180 + 12 = 192

8.  e)  11 × 53 = 530 + 53 = 583

9.	Calculate mentally.  That is, whatever you wrote in the previous problem, do mentally here.
	a)  12 × 9 = 90 + 18 = 108		b)  14 × 4 = 40 + 16 = 56
	c)  16 × 3 = 30 + 18 = 48		d)  18 × 5 = 50 + 40 = 90
	e)  16 × 9 = 90 + 54 = 144		f)  12 × 6 = 60 + 12 = 72
	g)  13 × 12 = 120 + 36 = 156		h)  15 × 7 = 70 + 35 = 105

10.	Multiplication by 11.  Calculate mentally.
	a)  11 × 15 = 150 + 15 = 165		b)  11 × 24 = 240 + 24 = 264
	c)  11 × 36 = 360 + 36 = 396		d)  11 × 49 = 490 + 49 = 539

11.  Calculate mentally.

10.  a)   27 × 3 = 60 + 21 = 81

10.  b)   32 × 6 = 180 + 12 = 192

10.  c)   45 × 5 = 200 + 25 = 225

10.  d)   64 × 9 = 540 + 36 = 576

12.	Zero
	a)	0 × 312 = 0		b)	9 × 0 = 0

Continue on to the next section.

or

Return to the previous section.

Table of Contents

---

Please make a donation to keep TheMathPage online.
We do not accept advertising. Even $1 will help.

---

Copyright © 2001-2007 Lawrence Spector

Questions or comments?

E-mail:  themathpage@nyc.rr.com