To solve problems like this, we must simply break it down and read each part carefully. We can also set it up as a math problem to make it easier to visualize.
The elevator starts on the twentieth floor, so we will represent that with 20.
20
It goes down 11 floors, so we can represent that with a -11.
20-11=9
Now we are on floor 9. Then, we go up 5 floors, so we can represent that with a 5.
9+5=14
Using the math above, we can see the elevator is on the 14th floor.
Answer:
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The answer is 4 pensioners
Answer:
D. difference of squares
Step-by-step explanation:
Both of the terms x^2 and 9 are squares, so their difference is the difference of squares. The factorization of that is a "special form" that can be usefully memorized.
a^2 -b^2 = (a -b)(a +b)
x^2 -9 = (x -3)(x +3)
So,
The probability of drawing a yellow marble is

.
Since he replaces the marble after it is drawn out, the probability of drawing another yellow is the same:

.
The probability of drawing a red marble is

.
In order to get the probability of drawing 2 yellow marbles and 1 red marble, given that each marble is replaced after it is drawn out, we must multiply the fractions together.

Because the order of the marbles doesn't matter, we will multiply the probability by 3.