Answer:
The year is 2020.
Step-by-step explanation:
Let the number of years passed since 2010 to reach population more than 7000000 be 'x'.
Given:
Initial population is, ![P_0=450,000](https://tex.z-dn.net/?f=P_0%3D450%2C000)
Growth rate is, ![r=5\%=0.05](https://tex.z-dn.net/?f=r%3D5%5C%25%3D0.05)
Final population is, ![P=700,000](https://tex.z-dn.net/?f=P%3D700%2C000)
A population growth is an exponential growth and is modeled by the following function:
![P=P_0(1+r)^x](https://tex.z-dn.net/?f=P%3DP_0%281%2Br%29%5Ex)
Taking log on both sides, we get:
![\log(P)=\log(P_0(1+r)^x)\\\log P=\log P_0+x\log (1+r)\\x\log (1+r)=\log P-\log P_0\\x\log(1+r)=\log(\frac{P}{P_0})\\x=\frac{\log(\frac{P}{P_0})}{\log(1+r)}](https://tex.z-dn.net/?f=%5Clog%28P%29%3D%5Clog%28P_0%281%2Br%29%5Ex%29%5C%5C%5Clog%20P%3D%5Clog%20P_0%2Bx%5Clog%20%281%2Br%29%5C%5Cx%5Clog%20%281%2Br%29%3D%5Clog%20P-%5Clog%20P_0%5C%5Cx%5Clog%281%2Br%29%3D%5Clog%28%5Cfrac%7BP%7D%7BP_0%7D%29%5C%5Cx%3D%5Cfrac%7B%5Clog%28%5Cfrac%7BP%7D%7BP_0%7D%29%7D%7B%5Clog%281%2Br%29%7D)
Plug in all the given values and solve for 'x'.
![x=\frac{\log(\frac{700,000}{450,000})}{\log(1+0.05)}\\x=\frac{0.192}{0.021}=9.13\approx 10](https://tex.z-dn.net/?f=x%3D%5Cfrac%7B%5Clog%28%5Cfrac%7B700%2C000%7D%7B450%2C000%7D%29%7D%7B%5Clog%281%2B0.05%29%7D%5C%5Cx%3D%5Cfrac%7B0.192%7D%7B0.021%7D%3D9.13%5Capprox%2010)
So, for
, the population is over 700,000. Therefore, from the tenth year after 2010, the population will be over 700,000.
Therefore, the tenth year after 2010 is 2020.
Answer:
117600
Step-by-step explanation:
50 x 49 x 48 = 117,600 ways
You have 50 possible for 1st, 49 for 2nd, 48 for 3rd
or
Permutations 50P3 = 117,600
Method OneYour calculator might be able to do this. Mine does it like this.
6
nCr
2
=
15
Method 2You could simply set up 6C2
This gives you
Method ThreeYou only have to do this a couple of times to see how the cancellation works.
![\frac{6!}{4!2!} = \frac{6*5*\st{4*3*2*1}}{4*3*2*1 * 2*1}](https://tex.z-dn.net/?f=%20%5Cfrac%7B6%21%7D%7B4%212%21%7D%20%3D%20%20%5Cfrac%7B6%2A5%2A%5Cst%7B4%2A3%2A2%2A1%7D%7D%7B4%2A3%2A2%2A1%20%2A%202%2A1%7D%20%20)
After all the cancellation takes place you have
6*5/2 = 15