If r is directly proportional to the square of s and r = 72 when = 12, find r when s = 8.?
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Answer:
3.61 seconds
Step-by-step explanation:
The bird starts 50 feet in the air, so will come down to a height of 40 feet after 3.61 seconds.
We want to solve h = 40.
40 = -16t^2 +55t +50
16t^2 -55t -10 = 0
t = (55 +√(55^2 -4(16)(-10)))/(2(16)) = (55 + √3665)/32 ≈ 3.61060
The bird will be 40 ft above the ground the first time after about 3.61 seconds.
The person would have to leave the money in the bank for 7.8 years for it to reach 13,500 dollars.
Step-by-step explanation:
Step 1; First we must calculate how much interest is generated for a single year. The annual interest rate is 4.5% i.e. 4.5% of 10,000 dollars which equals 0.045 × 10,000 = 450 dollars a year. As the years pass, more and more will be put into the account due to interest.
Step 2; For there to be 13,500 dollars in the bank account we need to calculate how much money is added due to interest.
The money needed to be added through interest = 13,500 - 10,000 = 3,500 dollars.
So we need to determine how long it will take for the bank to add 3,500 dollars by adding 450 dollars a year.
The number of years to reach 13,500 dollars = = 7.777 years. By rounding this value to the nearest tenth, we get 7.8 years.