Answer: 
Step-by-step explanation:
Here, According to the question, The population of the world is 4 billion (approx).
Again According to the question, The world's population has grown at an average rate of 1.9 percent per year since 1945.
Therefore, after 1975 the growth rate will remains same.
Thus, the population of the world after t years,
(By the formula 
)
⇒
Where 1.019 is the growth rate and 4 billion is the initial population.
Answer:
9/2π cm/s
Step-by-step explanation:
Volume of the spherical balloon V= 4/3πr³
Rate of change of volume dV/dt = dV/dr * dr/dt
dV/dr = 3(4/3πr²)
dV/dr = 4πr²
dV/dr = 4π(2)²
dV/dr = 16π
If V = 72cm²/s
72 = 16π*dr/dt
dr/dt = 72/16π
dr/dt = 9/2π cm/s
Hence the radius is changing at 9/2π cm/s
1220/8= 152.5
So 8 can go into 1220 152.5 times
To simplify 7C4 we use the combination formula given by:
nCr=n!/[(n-r)!r!]
thus:
In our case we shall have:
n=7 and r=4
7C4
=7!/[(7-4)!4!]
=5040/[6×24]
=5040/144
=35
The answer is 35
