A) The first step needs 100 bricks, the second needs 98, the third needs 96, and so on. Therefore the number of bricks for the nth step is: a_n = a_1 + d(n-1), where a_1 = 100 (the first term), d = -2 (difference).
a_n = 100 - 2(n-1) = 102 - 2n, and for the 30th step, a_30 = 102 - 2*30 = 42. So the top step will need 42 bricks.
b) The total staircase will need: 100 + 98 + 96 + ... + 44 + 42, and there are n = 30 terms. Using the formula for the sum of an arithmetic sequence:
S = (a_1 + a_n)*n/2 = (100 + 42)*30/2 = 2130
Therefore, 2130 bricks are required to build the entire staircase.
4.5x + 1.5y = 24 ⇒ 4.5x + 1.5y = 24
1.0x - 1.0y = 4 ⇒<u> 4.5x - 4.5y = 18</u>
<u>6y</u> = <u>6</u>
6 6
y = 1
4.5x + 1.5(1) = 24
4.5x + 1.5 = 24
<u> - 1.5 - 1.5</u>
<u>4.5x</u> = <u>22.5</u>
4.5 4.5
x = 5
(x, y) = (5, 1)
Alright, so you have the basic formula- good.
You have the A value (400), the interest rate r (7.5% -> .075 in decimal), and the final P value (8500). So, we only need to solve for t.
8500 = (400)(1+.075)^t
/400 /400
21.25 = 1.075^t
logarithms are the inverse of exponents, basically, if you have an example like
y = b^x, then a logarithm inverts it, logy(baseb)=x
Makes sense if you consider a power of ten.
1000 = 10^3
if you put logbase10(1000), you'll get 3.
Anyways, though, to solve the problem make a log with a base of 1.075 in your calculator
log21.25(base 1.075) = t
also, because of rules of change of base (might want to look this up to clarify), you can write this as log(21.25)/log(1.075) = t
Thus, t is 42.26118551.
Rounded to hundredths, t=42.26
Answer:
1.75
Step-by-step explanation:
If a and b are two numbers, then their arithmetic mean is
Given:
Divide this equation by 10:
Now, divide it by 2:
