Basic Mathematics for College Students

Chapter 4 Summary and Review 399

Perform each indicated operation.

29.

30.

31.

32.

33.

34.

35. 
    
    
    
    36. 
        
    
    
    
    


36. 
    
    
    
    38. Evaluate each expression.
    
    
    
    


37. 
    


38. 
    


39. a.Estimate the sum by rounding the addends to the
    nearest ten:
    b. Estimate the difference by using front-end
    rounding:289.4321.86

612.05145.006

(50.096)(0.035)

8.8(7.39.5)

3.55(1.25) 15.113.99

16.18.4 4.8(7.9)

8.61

5.97

 9.72

9,000.097,067.445

45.817.372

68.4753.3

3.46.78 35 0.008

19.534.412.8

42. COINS The thicknesses of a penny, nickel, dime,
    quarter, half-dollar, and presidential $1 coin are
    1.55 millimeters, 1.95 millimeters, 1.35 millimeters,
    1.75 millimeters, 2.15 millimeters, and 2.00
    millimeters, in that order. Find the height of a stack
    made from one of each type of coin.


43. SALE PRICES A calculator normally sells for
    $52.20. If it is being discounted $3.99, what is the
    sale price?


44. MICROWAVE OVENS A microwave oven is
    shown below. How tall is the window?

2.5 in.

2.75 in.

13.4 in.

2:17

123

456

78

POWERLEVEL 0

TIMECLOCK

LIGHT

AUTO

?? 9

REVIEW EXERCISES

SECTION 4.3 Multiplying Decimals

To multiply two decimals:

1.Multiply the decimals as if they were whole

numbers.

2.Find the total number of decimal places in both

factors.

3.Insert a decimal point in the result from step 1

so that the answer has the same number of

decimal places as the total found in step 2.

When multiplying decimals, we do notneed to line

up the decimal points.

DEFINITIONS AND CONCEPTS EXAMPLES

Multiply:

Write the problem in vertical form and multiply 2.76 and 4.3 as if

they were whole numbers.

Thus,2.764.311.868.

Move 3 places from right to left and insert

a decimal point in the answer.

The answer will have

2  1 3 decimal places.

v

2 decimal places.

1 decimal place.

2.76

 4.3

828

11040

11.868

2.764.3



Multiplying a decimal by 10, 100, 1,000, and so on

To find the product of a decimal and 10, 100, 1,000,

and so on, move the decimal point to the right the

same number of places as there are zeros in the

power of 10.

Multiplying a decimal by 0.1, 0.01, 0.001, and so on

To find the product of a decimal and 0.1, 0.01,

0.001, and so on, move the decimal point to the left

the same number of places as there are in the

power of 10.

Multiply:

Since 10,000 has fourzeros, move the

decimal point in 84.561 fourplaces to

the right. Write a placeholder zero

(shown in blue).

Multiply:

Since 0.01 has twodecimal places, move the

decimal point in 32.67 twoplaces to the

left.

32.670.010.3267

84.56110,000845,61 (^0)