83. 11.4 yr

85. 40 hr

87. At 5% compounded yearly, $A=\$9849.70.$ At 4.75% compounded monthly, $A=\$9754.74.$ The 5% investment will provide the greater return.

89.

1. 34 million

2. In 2206 (after 199.3 yr)

91.

1. 

2. $\approx 5\text{ hr}$

93. $t=6.57\text{ min }$

95.

1. 5000 people / square mile

2. 7459 people / square mile

3. $\approx 13.73\text{ miles}$

97. $I=0.2322I_0$

99.

1. 11.27 ft / sec

2. 5.29 ft / sec

3. 201

101.

1. 1 g

2. Remains stationary at 6 g

3. 4.6 days

103. 16 cents; yes, it is noticeable.

105. $4.0\cdot {10}^{-3};$ 1585 times more

107. 100 times more intense

109. $\approx 9.7$