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Ksju [112]
2 years ago
11

Find the sum of first 15 terms of an AP whose 4th and 9th t terms are -15 and -30 respectively.

Mathematics
1 answer:
Serga [27]2 years ago
7 0

Answer:

Sum of the first 15 terms = -405

Step-by-step explanation:

a + 3d = -15 (1)

a + 8d = -30 (2)

Where,

a = first term

d = common difference

n = number of terms

Subtract (1) from (1)

8d - 3d = -30 - (-15)

5d = -30 + 15

5d = -15

d = -15/5

= -3

d = -3

Substitute d = -3 into (1)

a + 3d = -15

a + 3(-3) = -15

a - 9 = -15

a = -15 + 9

a = -6

Sum of the first 15 terms

S = n/2[2a + (n − 1) × d]

= 15/2 {2×-6 + (15-1)-3}

= 7.5{-12 + (14)-3}

= 7.5{ -12 - 42}

= 7.5{-54}

= -405

Sum of the first 15 terms = -405

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Barry's final score is 45 which player had the greater final score?
natali 33 [55]

The player with the greater final score is of:

Barry.

<h3>How to obtain which player had the greater final score?</h3>

Barry's final score is given as follows:

45.

Then we have to obtain Lee's score, from the description given in the missing information section.

Lee's scored is obtained as follows:

  • Starts at -350.
  • Answers a 275-point question correctly, hence - 350 + 275 = -75.
  • Answers a 70 - point question correctly, hence -75 + 70 = -5.
  • Answers a 50 - point question incorrectly, hence: -5 - 50 = -55.

Thus Lee's final score is given as follows:

-55.

The classifications of the final scores according to the signals are given as follows:

  • Barry: positive score.
  • Lee: negative score.

A positive score will always be greater than a negative score, hence Barry had the greater final score.

<h3>Missing information</h3>

Lee and Barry play a trivia game in which questions are worth different numbers of points. If a question is answered correctly, a player earns points. If a question is answered incorrectly, the player loses points. Lee currently has -350 points.

a. Before the game ends, Lee answers a 275 -point question correctly, a 70 -point question correctly, and a 50 -polnt question incorrectly. Write and find the value of an expression to find Lee's final score.

b. Barry's final score is 45. Which player had the greater final score?

More can be learned about addition of measures at brainly.com/question/24342899

#SPJ1

5 0
1 year ago
a conical tank with vertex down is 10 feet across the top and 12 feet deep. If water is flowing out of the tank at a rate of 12
TiliK225 [7]

Answer:

The water level is dropping at a rate of 0.24 ft/s

Step-by-step explanation:

Here, we simply want to calculate the change in depth (height of the cone) , given the volume change

Mathematically, we have the volume of a cone as;

V = 1/3 * π * r^2 * h

we are given dv/dt as 12 ft^3/m

dv/dh = 1/3 * π * r^2

Substituting the value for the radius, we have

dv/dh = 1/3 * 22/7 * 4^2 = 50.29

dh/dt = dh/dv * dv/dt

dh/dv = 1/(dv/dh) = 1/50.29

Thus,

dh/dt = 1/50.29 * 12

dh/dt = 0.24 ft/s

3 0
2 years ago
Write as a decimal 23/9
Slav-nsk [51]

Answer:

2.555555555555.....

(the 5 is repeating)

Step-by-step explanation:

This is the answer because:

1) To convert the fraction to a decimal, you have to divide the numerator by the denominator.

2) Therefore, 23/9 is 2.5 (the 5 is repeating)

Hope this helps!

8 0
3 years ago
For the following equation, compute the x- and y- intercepts to graph the line.
nikklg [1K]
X-intercept: (-5,0)
Y-intercept: (0,4)
To solve for the X-Intercept, substitute 0 for y and solve for x.
To solve for the Y-Intercept, substitute 0 for x and solve for y.

7 0
3 years ago
Find the missing lengths:<br> LO=5 and OK=4, find OH and KH.
hodyreva [135]

Answer:

The length of KH is 6 units and OH is 6.3 units.

Step-by-step explanation:

Given the figure with lengths LO=5 and OK=4. we have to find the length of  OH and KH.

In ΔLOH

By Pythagoras theorem

LH^2=LO^2+OH^2\\\\LH^2=5^2+OH^2 → (1)

In ΔKOH,

KH^2=OH^2+OK^2\\\\KH^2=OH^2+4^2  → (2)

In ΔKHL,

KL^2=LH^2+KH^2

Using eq (1) and (2), we get

KL^2=5^2+OH^2+OH^2+4^2

9^2=25+2OH^2+16

⇒ 2OH^2=81-25-16=40

⇒ OH=\sqrt{20}=6.324\sim6.3units.

Put the above value in eq 2, we get

KH^2=20+4^2=36

⇒ KH=6 units.

8 0
3 years ago
Read 2 more answers
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