D. 9 cm because a times b equals c
<span>Hollis travels 0.05 miles per minute faster than Charmaine.
First, convert to the same units for both Hollis and Charmaine. So Hollis takes 18.5 minutes and Charmaine takes 0.5*60 = 30 minutes. Both girls travel 2.4 miles, so calculate how many miles per minute each takes
Hollis = 2.4 / 18.5 = 0.13 miles per minute.
Charmaine = 2.4 / 30 = 0.08 miles per minute.
Finally determine the difference in speed between the two girls.
0.13 - 0.08 = 0.05 miles per minute.</span>
First, start off by listing a few of the numbers that follow the first three clues to see if you can narrow it down.
7,111,111
7,333,333
7,555,555
etc.
Then, start adding up digits to see if you're getting close.
7+1+1+1+1+1+1 = 13
7+3+3+3+3+3+3 = 25
7+5+5+5+5+5+5 = 37
Since 7,555,555 is too high, we step it down to 7,555,333
7+5+5+5+3+3+3 = 31
7,555,333 will work as an answer, as well as 7,333,555, since it's the same amount when the digits are added together.
2n^2 + 4n + 2 = 0
Divide both sides by 2:
n^2 + 2n + 1 = 0
Find two numbers that multiply to form C (1) and add together to form 2: these numbers are 1 and 1:
(n +1)(n+1) = 0
(n+1)^2 = 0
Therefore n+1 = 0
n = -1