Answer:
A - Crest, B - amplitude, C - wavelength, D - trough
Explanation:
The answer to the problem b.
CaS is the empirical formula of the compound between calcium and sulphur that has the percent composition 55.6.
When percentages are given, we take a total mass of 100 grams.
Therefore the mass of each element is equal to the percentage given.
Mass of Ca = 55.6 g (given) of
S Mass = 44.4 g (100 - 55.6 = 44.4)
Step 1: Convert the given mass to moles.
moles Ca = given mass Ca / molar mass Ca
moles = 55.6 / 40 = 1.39 moles
mol S = specific mass S / molar mass S
mol = 44.4 / 32 = 1.39 mol
Step 2: Divide the molar ratio of each molar value by the smallest number of moles calculated.
For Ca = 1.39 / 1.39 = 1
For S = 1.39 / 1.39 = 1
The ratio of Ca : S = 1:1
Hence the empirical formula of the given compound will be CaS.
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Answer:

negative sign indicates that the distance is decreasing with time
Explanation:
Let at any time t after noon that is 12 p.m.
distance traveled by car A = 40t
distance traveled by car B = 90-60t
then distance between the two cars at time t
............1
also, at time 1 p.m.
distance 
D=50 Km
differentiating equation 1 w.r.t. t we get

put t= 1 and D= 50 we get

