MULTIPLY WHOLE NUMBERS,
MULTIPLY DECIMALS

PROBLEMS

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  1. 213
  × 342
  426
  8526
  63926

a)   In the partial product 852, in which place is 2?

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Tens.

Why?

Because we multiplied by 4 tens.

b)   In the partial product 639, in which place is 9?

Hundreds.

Why?

Because we multiplied by 3 Hundreds.

a)  8 × 9 = 72.   What does the carried 7 signify?   7 tens.

b)  8 × 5 = 40, plus 7 = 47.  What does the carried 4
b)  signify?   4 hundreds.

b)   Why?  Because we are multiplying 8 × 5 tens = 40 tens, plus 7 tens = 47 tens = 470.

  3.   a)    43   b)    57 c)    236 d)    709
× 26   × 45 × 78 × 39
1118   2565 18,408 27,651
  4.   a)    532   b)    806 c)    706
× 321   × 674 × 456
170,772   543,244 321,936
 
       d)    666   e)    895 f)    907
× 302   × 402 × 609
201,132   359,790 552,363

Multiplying decimals

5.    23 × 584 = 13432.

18.  Therefore,

5.     a)  2.3 × .584 = 1.3432

5.  b)  .0023 × 5.84 = .013432

6.   a)   If we ignore the decimal point in 4.58 and consider it as 458, what
6.   a)   have we actually done to 4.58?

Multiplied by 100.

6.   b)  If we separate two decimal digits in 458 so that it becomes 4.58,
6.   a)   what have we actually done to 458?

Divided by 100.

7.  Do not calculate vertically.  Just write the answer.

.3 × .03 = .009   .004 × .02 = .00008
 
.003 × .015 = .000045   .00404 × 2 = .00808
 
.04 × .00101 =  .0000404   .16 × .002 = .00032
 
.3 × .028 =  .0084   .05 × 76 =  3.8
 
9.3 × .008 =  .0744   2 × .0067 =  .0134

 8.  Do not calculate vertically.

11. a)  200 × 1.6   200 × 16 = 3200.  200 × 1.6 = 320.0 = 320

11. b)  3000 × .07 = 210

11. c)  50 × .11 = 5.5             d)  .008 × 900 = 7.2

11. e)  .6 × 7000 = 4200         f)  .0003 × 25,000 = 7.5

 9.  School lunches cost $12.50 a week.

09. a)   How much will 6 weekly lunches cost?

On distributing 6:

6 × 12.50 = 6 × 12  +  6 × .50
  = 72 + 3.00  (Lesson 9)
  = $75.00

09. a)   How much will 10 weekly lunches cost?

10 × $12.50 = $125.00.  (Lesson 4)

10.  A photocopy costs 3 cents a sheet.  If a business makes 12,000 copies
19.  a year, what is their cost?

3 × 12,000 = 36,000.  $.03 × 12,000 = $360.00

11.  Jane earns $7.50 an hour.  What is her pay for a 40 hour week?  $300

11.  What is her yearly pay?  52 × $300 = $15,600

12.  The circumference of a circle C is related to the diameter D as
12.  follows:

C = 3.14 × D

How long is the circumference if the diameter is 1.6 inches?

3.14 × 1.6 = 5.024 inches

13.  Calculate the area of a rectangle whose base is 2.5 cm and whose
13.  height is .38 cm.

2.5 cm × .38 cm = 0.95 cm²

14.  How much is
14.  a)   3% of $64?   $1.92   b)   6% of $83?   $4.98  
 
14.  c)   7% of $124?   $8.68   d)   8% of $324?   $25.92  

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