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Alecsey [184]
3 years ago
13

A group of students calculated their average score at a spelling bee. They realized that if one of them scored 9 more points, th

eir average score would be 81 points. If one of them scored 3 points less, their average score would be 78 points. How many students were in the group?
Mathematics
1 answer:
alukav5142 [94]3 years ago
8 0

Answer: There are 4 students in the group.

Step-by-step explanation:

Let the number of students in the group be n

If one of them scored 9 more points , their average score would be 81 points.

So, our equation (1) will be

\frac{\sum x+9}{n}=81\\\\\sum x+9=81n

Similarly,

If one of them scored 3 points less, their average score would be 78 points.

So, our equation (2) will be

\frac{\sum x-3}{n}=78\\\\\sum x-3=78n

So, from equation (1) and (2) we get:

81n-9=\sum x=78n+3\\\\81n-9=78n+3\\\\81n-78n=3+9\\\\3n=12\\\\n=\frac{12}{3}\\\\n=4

Hence, there are 4 students in the group.

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A lawyer has found 60 investors for a limited partnership to purchase an inner-city apartment building, with each contributing e
Mars2501 [29]

Answer:

1.  The lawyer has 34 investors that contribute with $3,000 and has 26 investors that contribute with $6,000.

2. The jar has 26 nickels and 44 dimes that worth $5.70.

3. The concession stand has sold 1600 sodas and 1400 hotdogs

Step-by-step explanation:

For all the problems we are going to follow the same process that will consist on 1. Define the variables. 2. Formulate the system of two linear equations 3. Solve by the elimination method 4. Give the answer.

  • First problem.

- Variables:

x = number of investors that contribute with $3,000

y = number of investors that contribute with $6,000

- System of equations.

First equation will be the result of adding the number of investors that will give us a total of 60 investors then:

x + y = 60

Second equation is the result of multypling the number of investors by its invest and adding between them to get the $258,000 they have raised:

3,000x + 6,000y = 258,000

The system will be:

x + y = 60

3,000x + 6,000y = 258,000

- Solve by the elimination method.

To cancel x we are going to multiply by -3000 in both sides of the first equation and we will leave the second equation the same but in the first row to make easier the calculations then:

3,000x + 6,000y = 258,000

(x + y ) (-3,000) = 60 (-3,000) <em>   solve the multiplications </em>

3,000x + 6,000y = 258,000

<u>-3,000x - 3,000y = -180,000 </u><em>   solve the operations</em>

0 + 3,000y = 78,000     <em>clear y</em>

y = \frac{78,000}{3,000}    <em>solve the division</em>

y = 26

For calculate x, replace the y value in the first equation and solve it

x + 26 = 60

x = 60 - 26

x = 34

- Answer

The lawyer has 34 investors that contribute with $3,000 and has 26 investors that contribute with $6,000.

  • Second problem

- Variables:

x = number of nickels

y = number of dimes

- System of equations.

First equation will be the result of adding the number of nickels and dimes that will give us a total of 70 coins in the jar then:

x + y = 70

Second equation is the result of multypling the number of coins by its value and adding between them to get the $5.70 that the jar worth:

0.05x + 0.1 y = 5.70

The system will be:

x + y = 70

0.05x + 0.1 y = 5.70

- Solve by the elimination method.

To cancel x we are going to multiply by -0.05 in both sides of the first equation and we will leave the second equation the same but in the first row to make easier the calculations then:

0.05x + 0.1 y = 5.70

(x + y ) (-0.05) = 70 (-0.05) <em>   solve the multiplications </em>

0.05x + 0.1 y = 5.70

<u>-0.05x - 0.05y = -3.50 </u><em>   solve the operations</em>

0 + 0.05y = 2.20     <em>clear y</em>

y = \frac{2.20}{0.05}    <em>solve the division</em>

y = 44

For calculate x, replace the y value in the first equation and solve it

x + 44 = 70

x = 70 - 44

x = 26

- Answer

The jar has 26 nickels and 44 dimes that worth $5.70.

  • Third problem.

- Variables:

x = number of sodas sold by $2

y =  number of hotdogs sold by $3

- System of equations.

First equation will be the result of adding the number of sodas and hotdogs that is of 3000 then:

x + y = 3000

Second equation is the result of multypling the number of sodas and hotdogs by its price and adding between them to get the $7400 of the receipts:

2x + 3y = 7400

The system will be:

x + y = 3000

2x + 3y = 7400

- Solve by the elimination method.

To cancel x we are going to multiply by -2 in both sides of the first equation and we will leave the second equation the same but in the first row to make easier the calculations then:

2x + 3y = 7400

(x + y ) (-2) = 3000 (-2) <em>   solve the multiplications </em>

2x + 3y = 7400

<u>-2x - 2y = -6000 </u><em>   solve the operations</em>

0 + 1y = 1400     <em>clear y</em>

y = \frac{1400}{1}    <em>solve the division</em>

y = 1400

For calculate x, replace the y value in the first equation and solve it

x + 1400 = 3000

x = 3000 - 1400

x = 1600

- Answer

The concession stand has sold 1600 sodas and 1400 hotdogs

6 0
3 years ago
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