As per as the Multiplication rules of the significant figures, whenever any numbers in the decimals forms are multiplied or divided then result in mentioned in such a way so that the significant figures after the decimal will be same as that in the given least condition.
_______________________________
102900/12 = 8575
170 × 1.27 = 215.9
∴ (102,900 ÷ 12) + (170 × 1.27) =  8575 + 215.9
= 8790.9
Now, As per as Above rules, answer in correct significant figures will be = 8791. 
 
        
             
        
        
        
Answer:
9.8×10^-4...... is the answer
 
        
             
        
        
        
 
Answer:
A sample of a gas (5.0 mol) at 1.0 atm is expanded at constant temperature from 10 L to 15 L. The final pressure is 0.67 atm.
Step by Step Explanation?
Boyle's law states that in constant temperature the variation volume of gas is inversely proportional to the applied pressure.
The formula is,
P₁ x V₁ = P₂ × V₂
Where,
P₁ is initial pressure = 1 atm
P2 is final pressure = ? (Not Known)
V₁ is initial volume = 10 L
V₂ is final volume = 15 L
Now put the values in the formula,
\begin{gathered}\rm 1\times 10 = P_2\times 15\\\\\rm P_2 = \frac{10}{15\\} \\\\\rm P_2 = 0.67\end{gathered]
Therefore, the answer is 0.67 atm. 
 
        
                    
             
        
        
        
Answer:
Mason notices that his boat sinks lower into the water in a freshwater lake than in the ocean. What could explain this?
Explanation:
The freshwater has less density then the ocean!
 
        
             
        
        
        
Al4C3 + 12H2O-----> 3CH4 + 4Al(OH)3