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3 years ago

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A problem states that Ursula earns $9 per hour. To write an expression that tells how much money Ursula earns for h hours, Joshu

a wrote 9 divided by h. Sarah wrote 9h. Whose expression is correct and why?

1 answer:

LekaFEV [45]3 years ago

8 0

The correct one would by 9h because you are asking how much will Ursula make per hour. So let's say that h is 10, then in order to know how much Ursula makes per hour, you have to add 9 ten times. A short way to do that would be to simply multiply 9 with 10 so that you can get the answer of 90. It cannot be 9/h because then answer will be much lower than it is supposed to be. So the answer to the question is really 9h.

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1) Omar has scored 85, 71, and 77 on the first three exams in his math class. If the standard 70,80,90 scale is used for grades

Rus_ich [418]

Answer:

a. 47

b. 87

c. 127

Step-by-step explanation:

Assume a total of 4 exams ( first 3 plus a final)

Let final score be X,

Hence, average score = (85 + 71 + 77 + x) / 4 = (233 + x) / 4

a) to get a C, the average score must be 70

70 = (233 + x) / 4

(233 + x) = 70 (4) = 280

x = 280 - 233 = 47 (Ans)

b) to get a B, the average score must be 80

80 = (233 + x) / 4

(233 + x) = 80 (4) = 320

x = 320 - 233 = 87 (Ans)

c) to get a A, the average score must be 90

90 = (233 + x) / 4

(233 + x) = 90 (4) = 360

x = 360 - 233 = 127 (Ans)

6 0

3 years ago

Determine all prime numbers a, b and c for which the expression a ^ 2 + b ^ 2 + c ^ 2 - 1 is a perfect square .

kogti [31]

Answer:

The family of all prime numbers such that $a^{2} + b^{2} + c^{2} -1$ is a perfect square is represented by the following solution:

$a$ is an arbitrary prime number. (1)

$b = \sqrt{1 + 2\cdot a \cdot c}$ (2)

$c$ is another arbitrary prime number. (3)

Step-by-step explanation:

From Algebra we know that a second order polynomial is a perfect square if and only if $(x+y)^{2} = x^{2} + 2\cdot x\cdot y + y^{2}$ . From statement, we must fulfill the following identity:

$a^{2} + b^{2} + c^{2} - 1 = x^{2} + 2\cdot x\cdot y + y^{2}$

By Associative and Commutative properties, we can reorganize the expression as follows:

$a^{2} + (b^{2}-1) + c^{2} = x^{2} + 2\cdot x \cdot y + y^{2}$ (1)

Then, we have the following system of equations:

$x = a$ (2)

$(b^{2}-1) = 2\cdot x\cdot y$ (3)

$y = c$ (4)

By (2) and (4) in (3), we have the following expression:

$(b^{2} - 1) = 2\cdot a \cdot c$

$b^{2} = 1 + 2\cdot a \cdot c$

$b = \sqrt{1 + 2\cdot a\cdot c}$

From Number Theory, we remember that a number is prime if and only if is divisible both by 1 and by itself. Then, $a, b, c > 1$ . If $a$ , $b$ and $c$ are prime numbers, then $2\cdot a\cdot c$ must be an even composite number, which means that $a$ and $c$ can be either both odd numbers or a even number and a odd number. In the family of prime numbers, the only even number is 2.

In addition, $b$ must be a natural number, which means that:

$1 + 2\cdot a\cdot c \ge 4$

$2\cdot a \cdot c \ge 3$

$a\cdot c \ge \frac{3}{2}$

But the lowest possible product made by two prime numbers is $2^{2} = 4$ . Hence, $a\cdot c \ge 4$ .

The family of all prime numbers such that $a^{2} + b^{2} + c^{2} -1$ is a perfect square is represented by the following solution:

$a$ is an arbitrary prime number. (1)

$b = \sqrt{1 + 2\cdot a \cdot c}$ (2)

$c$ is another arbitrary prime number. (3)

Example: $a = 2$ , $c = 2$

$b = \sqrt{1 + 2\cdot (2)\cdot (2)}$

$b = 3$

4 0

3 years ago

Please help I’m so close to passing math

kirill115 [55]

Answer:

$0.14 per ounce of salsa

Step-by-step explanation:

2.80/20

Move decimal to make the number a whole number

(Have to move the decimal the same amount of spaces)

28/200

0.14

Hope this helps. Have a nice day

8 0

2 years ago

Read 2 more answers

Amanda is a cabinetmaker. She makes cabinets using one of three types of wood: birch, maple, or cherry. She can finish each type

padilas [110]

Assume that each material in each category has an equal chance of being selected.

Categories:
(a) Type of wood used to make the cabinet: birch, maple, cherry.
Each type of wood has a probability of 1/3 to be selected.
(b) Type of finish: transparent, semi-transparent.
Each type of finish has a probability of 1/2 to be selected.
(c) Knob: bronze, steel, wood.
Each material has 1/3 probability to be selected.

Each event (selecting material for the cabinet, for the finish, and for the knob) is an independent event.

Therefore
Probablity(birch wood AND bronze knob) = (1/3)*(1/3) = 1/9
Probability(wood knob) = 1/3
Probability(transparent stain) = 1/2
Probability(cheryy wood AND semi-transparent stain) = (1/3)*(1/2) = 1/6

6 0

3 years ago

Round to the nearest cent $6.51

son4ous [18]

Answer: $6.50
If the number is below 5 (so 1-4) you round down. If its above 5 (5-9), you round up.
E.G. 78.89
Round this to the nearest 10th, you'll get 78.90

4 0

3 years ago