Here were the choices on that question:
a. poverty
b. lack of adequate rivers
c. mountains
<span>d. richness
The answer is D. richness. Based on A Companion to World History, the African Sahel can be a corridor of communication between Nile and Niger valleys but did not materialize. The reason was the richness of Sahel that it that it can provide for itself even without trade.
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Set this up as
10 = 40 (1/2)t/28
and solve for t in years.
10/40 = (1/2)t/28
log(0.25) = (t/28) log(0.5)
t = 28 log(0.25) / log(0.5) years = 56 years
Test the answer:
56 years = 2(28 years) = 2 half-lives, so the remaining amount should be 1/2 of 1/2 of the initial amount, i.e. 1/4 of the initial amount, and 10 mg = 1/4 of 40 mg.
A. Silt is no longer carried down river.
Answer:
Clouds form when air reaches its dew point. This can happen in two ways:
(1) Air temperature stays the same but humidity increases. This is common in locations that are warm and humid.
(2) Humidity remains the same, but temperature decreases
