The number is written in scientific notation.
The significant figures are the numbers known precisely plus 1 digit that is uncertain.
When the numbers are expressed in scientific notation all the digits before  10^n are significant.
So, 7 and 8 are significant figures and the answer is that the number of significant figures is 2.
Answer: 2
        
             
        
        
        
Answer:
 6.45 joules
Explanation:
energy=10×(55-50)×0.129
=1.29×5
=6.45 J
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Answer:
 Ventilators are provided in the rooms at the top of the roofs because if the air inside the room gets hot, the hot air rises up and flows through these ventilators and thus cool air remains at bottom. Thus ventilators maintain conventional currents to keep the air fresh in the room.
Explanation:
 
        
                    
             
        
        
        
Q=m(c∆t +heat of fusion + heat of evaporation)
m= 44g 
c= 4.186 J/g.C
∆t= 107-(-8) =115 C
heat of fusion= 333.55 J/g
heat of evaporation=2260 J/g
Q=44(4.186*115 + 333.55 + 2260)
Q= 135297.36 J