1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Ksju [112]
2 years ago
5

In a theater, there are 15 chairs in the first row, each row has 3 more chairs than the previous row, and there are 15 rows. how

many chairs are there in the theater?
SAT
1 answer:
Nimfa-mama [501]2 years ago
5 0

The 1st row has 15 chairs.

The 2nd row has 15 + 3 = 18 chairs.

The 3rd row has 18 + 3 = 15 + 2•3 = 21 chairs.

The 4th row has 21 + 3 = 15 + 3•3 = 24 chairs.

The pattern continues, so that the n-th row has 15 + (n - 1)•3 = 3n + 12 chairs.

If there are 15 rows, then the total number of chairs is

\displaystyle \sum_{n=1}^{15} (3n + 12) = 3 \sum_{n=1}^{15} n + 12 \sum_{n=1}^{15} 1 = 3\cdot\frac{15\cdot16}2 + 12\cdot15 = \boxed{540}

where we use the formulas

\displaystyle \sum_{n=1}^N 1 = N

\displaystyle \sum_{n=1}^N n = \frac{N(N+1)}2

You might be interested in
How does the author develop Miss Havisham's
saveliy_v [14]

Answer:

by using descriptive phrases such as with strong emphasis and with a weird smile

Explanation:

3 0
3 years ago
Maya is playing a game with multiple choice questions. each question has 2 correct answers among 5 answer choices
Tasya [4]

Answer: .3 or 3/10

Explanation: The probability that her first answer is correct is 2/5. Since she got the first guess correct, now there is only 1 correct answer out of 4. There is a 3/4 chance she will get the next problem wrong

So: 2/5 x 3/4 = .3

8 0
3 years ago
Assume that there is a 6​% rate of disk drive failure in a year. a. If all your computer data is stored on a hard disk drive wit
Finger [1]
The easiest way to do this is calculate the probability that all drives crash, and subtract that from one. The first one is .06 squared subtracted from 1, so it’s .9964 or 99.64%. The second one is .06 cubed subtracted from 1, so it’s .9998, or 99.98 %
3 0
3 years ago
I have 2 warnings :)
mrs_skeptik [129]

Answer:

for what?? what happened

7 0
4 years ago
Read 2 more answers
Speed, Velocity or Acceleration?
qaws [65]

Answer:

Acceleration

Explanation:

Speed is how fast something moves.

Velocity is how fast it moves and in what direction it moves in.

Acceleration is the change in how fast it moves. I.e. if it speed up or slows down.

Here we are not given a speed, but are told that the subway car slows down (a negative change in speed), which is a change in speed, therefore it is acceleration (or more accurately deceleration as it is negative acceleration, slowing down, but acceleration is usually used to describe both.)

Hope this helped!

5 0
3 years ago
Other questions:
  • What is the first step in the armys CRM?
    11·1 answer
  • At the circle justice meeting, who's voice made
    11·1 answer
  • Which of the following fees would likely be the highest
    10·2 answers
  • Which of the following is offered by companies, organizations, an agencies to ensure a good range of potential employees ?
    12·2 answers
  • During last year's basketball season, Jackson attempted
    5·1 answer
  • Which of the following does not represent an attribute of the function f(x) = |x|?.
    10·1 answer
  • The total cost of renting a car is $30. 00 for each day the car is rented plus 28 1/2 ¢ for each mile the car is driven. What is
    13·1 answer
  • Select two ideas that the metaphor of the veil emphasizes in
    8·1 answer
  • Which of the following are used in the production of smartphones? select the three correct answers.
    7·1 answer
  • The table of values shows the height of a car of a ferris wheel
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!