PART A:
Scientific notation is given by A×10ⁿ where A is any number in a unit and 'n' is an integer.
0.000025 = 2.5×10⁻⁵
PART B:
Diameter of grain of sand ÷ Diameter of human body average cell
(2×10⁻⁴) ÷ (1×10⁻⁵) 
(2÷1) × (10⁻⁴÷10⁻⁵)
2 × (10⁻⁴ ⁻ ⁻⁵) = 2 × 10⁽⁻⁴⁺⁵⁾ = 2 × 10¹ = 20 times bigger
PART C:
The diameter of human body's average cell in nanometer
1 × 10⁻⁵ metre = 1 × 10⁻⁵ × 10⁹ = 1 × 10⁽⁻⁵⁺⁹⁾ = 1 × 10⁴ nanometer
PART D:
Smallest bacteria = 300 nanometer
300 nm = 300 ÷ 10⁹ = (3 × 10²) ÷ 10⁹ = 3 × (10²⁻⁹) = 3 × 10⁻⁷ meter
PART E:
Laws of exponents that are applied in scientific notation is 
xᵇ × xᵃ = x⁽ᵇ⁺ᵃ⁾
xᵇ ÷ xᵃ = x⁽ᵇ⁻ᵃ⁾
        
             
        
        
        
Answer:
1 hr, 48 minutes
Step-by-step explanation:
you can create a proportion:
doughnuts/hours = doughnut/hours (h)
1500/9 = 300/h
cross-multiply to get:
1500h = 2700
h = 27/15
h = 1 12/15, which is 1 hr, 48 minutes because 12/15 = 48/60
 
        
             
        
        
        
Answer: 66.50+5g= 83.50
g=3.4 
Step-by-step explanation: