This is just like an exponential growth equation...
Final=initial*rate^periods
25000=12500(1.0525)^t
2=1.0525^t
ln2=t ln1.0525
t=ln2/ln1.0525
t=13.55
t=14 yrs
17 - 6 = 11
11 * 2 = 22
22 + 6 = 28
Weekly allowance = $28
I'll get you started:
mean = np = (500)(.56) = ?
standard deviation = √npq = √(500)(.56)(.44) = ?
Note: q = 1 - p
Finish the calculations.
To find z-score:
z = (x - mean)/sd
Note: x = 250
Once you have the z-score, look in a z-table using the score to find your probability. Remember that the question is asking "at least 250" when looking at the table.
10% of $20 is 2 so the shirt would be $18 before tax
