So if you take a 39 ft ladder and place its base 15 feet from the base of the wall, when you lean the ladder against the wall, the point where the ladder rests against the wall will be 36 feet above the ground.
Answer: 15 feet
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Hope this helps you understand this problem a little better.
Answer : The amount of formaldehyde permissible are, 
Explanation : Given,
Density of air =

First we have to calculate the mass of air.



Now we have to calculate the amount of formaldehyde.
Permissible exposure level of formaldehyde = 0.75 ppm = 
Amount of formaldehyde in 7.2 g of formaldehyde = 
Amount of formaldehyde in 7.2 g of formaldehyde = 
Thus, the amount of formaldehyde permissible are, 
The answer is b but you want to think of why it is moving fast because of the temp indication
Answer: Option (B) is the correct answer.
Explanation:
It is known that for writing a chemical reaction equation, reactants are written on left hand side whereas products are written on right hand side.
And in between reactants and products a forward arrow is placed pointing towards the products.
Therefore, the reaction for carbon burns in the presence of oxygen to give carbon dioxide will be written as follows.

Here, carbon and oxygen atoms are the reactants whereas carbon dioxide is the product.
i believe the answer is...
Atoms of isotopes of an element have different numbers of protons.