Answer:
The least possible number of coins that Pirate Jack has is 77.
Step-by-step explanation:
i) let the number of coins in the piles for the parrots be x.
ii) therefore we can say that the total number of coins be 7x + 4
iii) let the number of coins in the piles for for the pirates be y.
iv) therefore we can say that the total number of coins be 11y + 4
v) therefore we can say that 7x + 4 = 11y + 4
vi) therefore 7x = 11y
vii) therefore the least possible number of coins that Pirate Jack has is equal to the LCM of 11 and 7 which is 77.
viii) x = 11 and y = 7
Position in the sequence triangular number relation
1 1 1 = 1*(1+1)/2
2 3 3 = 2(2+1)/2
3 6 6 = 3(3+1)/2
4 10 10 = 4(4+1)/2
5 15 15= 5(5+1)/2
Call n the position in the sequence, then the triangular number is: n(n+1)/2
Answer: Jacob is 7 years old.
Step-by-step explanation: 5 years ago, Jacob was 2 years old and his brother was 12. Now, in three years, Jacob will be 10 and his brother will be 20. To find the answer, you need a system of equations. The first equation will be 6(J-5) = B - 5, where J is Jacob's current age and B is his brother's. The next equation will be 2(J + 3) = B + 3. Now, just solve the equation. I gave you the answer, but please work through the problem so you understand it :D
There is a relationship between confidence interval and standard deviation:

Where

is the mean,

is standard deviation, and n is number of data points.
Every confidence interval has associated z value. This can be found online.
We need to find the standard deviation first:

When we do all the calculations we find that:

Now we can find confidence intervals:

We can see that as confidence interval increases so does the error margin. Z values accociated with each confidence intreval also get bigger as confidence interval increases.
Here is the link to the spreadsheet with standard deviation calculation:
https://docs.google.com/spreadsheets/d/1pnsJIrM_lmQKAGRJvduiHzjg9mYvLgpsCqCoGYvR5Us/edit?usp=sharing