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1) No, it is not a proper answer; you do not know whether the professor meant homework problem number 20 or 20 homework problems. Twenty is a quantity and does not make sense without a unit

3)

Middle Zeros: Zeros that appear between other nonzero digits are ALWAYS significant.

Leading Zero: Zeros that appear in front of all nonzero digits are NEVER significant.

Trailing Zero with a decimal point: Trailing zeros in a number with a decimal point are significant.

Trailing Zero without a decimal point: Trailing zero in a number without a decimal points are ambiguous.

5) A conversion factor is a fraction whose numerator and denominator. The system is set up will result in the units in numerator and denominator cancels leaving behind the desire unit.

Scientific Notation

7) a)1.0000 x 108 b) 4.970 x 10-4  c)3.001 x 101 d) 2.500 x 103

9) a) 7.36350 x 105    b)3.9 x 10-3   c) 2.500 x 103 d) 4.78 x 10-1

11) a) 86200 b) 0.0055 c) 0.00000102 d) 0.000000000603

13) a) 4700 b) 7.410 x 103 c) 0.00093 d) 4.5 x 10-3

15) a) 840,000 b) 5.13 x 102 c) 0.00000630 d) 2.50 x 10-1

Significant Figures

17) a) 6.46 cm b) 33.5 mL c) 6.28 mL

19) a) 6 SF    all non-zeros are significant

all leading zeros are not significant

all middle zeros are significant

all trailing zeros with a decimal point are significant

b) 6 SF   all non-zeros are significant

all middle zeros are significant

c) 6 SF   all non-zeros are significant

all trailing zeros with a decimal point are significant

d) 3 SF   all non-zeros are significant

all leading zeros are not significant

21) a) 6 SF    all non-zeros are significant

all leading zeros are not significant

all middle zeros are significant

all trailing zeros with a decimal point are significant

b) 6 SF   all non-zeros are significant

all middle zeros are significant

c) 6 SF   all non-zeros are significant

all trailing zeros with a decimal point are significant

d) 3 SF   all non-zeros are significant

all leading zeros are not significant

23) a) 5 SF b) 4 SF c) 4 SF d) 4 SF

Rounding

25) a) 24.6 b) 0.342 c) 4.35 x 104 d) 7.00 x 103

27) a) 5.65 x 101 b) 8.90 x 108 c) 1.00 x 106 d) 0.984

29) a) incorrect; 4.56 x 103 b) incorrect; 8.51 x 103  c) correct d) incorrect; 0.0531

31) b) 216.4, 2.2 x 102, 2 x 102

c) 0.3668, 0.37, 0.4

d) 0.008889, 0.0089, 0.009

33) b) 654.9, 6.5 x 102, 7 x 102

c) 0.7513, 0.75, 0.8

d) 0.007778, 0.0078, 0.008

Significant Figures in Calculations

35) a) 4986.2 b) 1.1 c) correct d) 0.154

37) a) 55 b) correct c) 0.86 d) 0.001

39) a) 48 b) 2597 c) correct d) 0.009

41) a) correct b) 6.220 x 103 c) 136 d) 4.5315

Unit Conversion

43) a) 1.000 x 106 mg b) 6.981 x 10-6 m c) 1.5 x 10-2 L d) 3.45 x 103 mm

45) a) 3.4 x 104g b) 7.53934 x 10-6 m c) 3.6 x 103 cL d) 1.09 x 103 mm

47) a) 4.76 x 104 mm b) 6.71 kg c) 0.248 mi d) 30.5 cm

49)

 m km mm nm pm 6.02 x10-5 m 6.02 x 10-8 km 6.02 x 10-2 mm 6.02 x 104 nm 6.02 x 107 pm 2.53 x 10-11 m 2.53 x 10-14 km 2.53 x 10-8 mm 0.0253 nm 25.3 pm 2.25 x 10-7 m 2.25 x 10-10 km 0.000225 mm 225 nm 2.25 x 105 pm 8.22 m 8.22 x 10-3 km 8.22 x 103 mm 8.22 x 109 nm 8.22 x 1012 pm 4.20 x 102 m 0.42 4.2 x 105 mm 4.2 x 1011 nm 4.2 x 1014 pm

51)

 m km mm nm pm 1.88 x10-5 s 1.88 x 10-8 km 1.88 x 10-2 mm 1.88 x 104 nm 1.88 x 107 pm 1.43 x 10-11 m 1.43 x 10-14 km 1.43 x 10-8 mm 0.0143 nm 14.3 pm 3.65 x 10-7 m 3.65 x 10-10 km 0.000365 mm 365 nm 6.65 x 106 pm 6.34 m 6.34 x 10-3 km 6.34 x 103 mm 6.34 x 109 nm 6.34 x 109 pm 6.9 x 102 m 6.9 km 6.9 x 105 mm 6.9  x 108 nm 6.9 x 1011 pm

Unit Raised to a Power

53) a) 3.5 x 102 in2 b) 2.2 x 101 ft2 c) 3.1 yd3

55) a) 5.33 x 103 in2 b) 3.44 x 106 mm c) 3.44 x 10-6 km

57) a) 2.09 x 104 in2 b) 1.35 x 107 mm2 c) 1.35 x 10-5 km

Density

59) 11.33 g/mL, yes

61) a) 2.34 x 103 g b) 69.1 cm3

63) a) 6.894 x 103 g b) 70.76 cm3

Cumulative Problems

65) \$63.54

67) 6.52 x 103 h

69) 32.5 lb of apples