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chubhunter [2.5K]

2 years ago

3

Stefan's family rented a rototiller to prepare an area in their backyard for spring planting. The rental company charged an init

ial fee of $43 with an additional fee per hour. If they paid $64 after renting the rototiller for 7 hours, what was the hourly fee?

2 answers:

drek231 [11]2 years ago

6 0

Answer:

The hourly fee is $ 3.

Step-by-step explanation:

Given,

The initial fee = $ 43,

Let x be the additional hourly fee ( in dollars ),

Thus, the total additional fee for 7 hours = 7x dollars,

And, the total fee for 7 hours = Initial fee + Additional fee for 7 hours

= ( 43 + 7x ) dollars,

According to the question,

43 + 7x = 64

7x = 21 ( Subtracting 43 on both sides )

x = 3 ( Divide both sides by 7 )

Hence, the hourly fee is $ 3.

taurus [48]2 years ago

6 0

3rd Option: 7h + 43 =64

2nd Option: $3

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You have 64 coins, consisting of pennies, nickels, and quarters. The value of

Romashka-Z-Leto [24]

Answer:

There are 20 pennies, 33 nickels and 11 quarters

Step-by-step explanation:

- You have 64 coins, consisting of pennies, nickels, and quarters

- The value of the coins is $4.60

- Assume that there are p pennies, n nickles, and q quarters

∴ p + n + q = 64 ⇒ (1)

- Lets find the value of each types of coins

∵ 1 penny = 1 cent ⇒ p = p cents

∵ 1 nickel = 5 cents ⇒ n = 5n cents

∵ 1 quarter = 25 cents ⇒ q = 25q cents

∵ 1 dollar = 100 cents ⇒ $4.60 = 4.60 × 100 = 460 cents

∴ p + 5n + 25q = 460 ⇒ (2)

- You also know that you have three times as many nickels as quarters

∴ n = 3q ⇒ (3) ⇒ the number of nickles by quarters

∵ 5n = 5(3q)

∴ 5n = 15q ⇒ (4) ⇒ the values of nickles by quarters

- Substitute (3) in equation (1) and (4) in equation (2)

∴ p + 3q + q = 64

∴ p + 4q = 64 ⇒ (5)

∴ p + 15q + 25q = 460

∴ p + 40q = 460 ⇒ (6)

- Subtract equation (5) from equation(6) to eliminate p

∴ 36q = 396

- Divide both sides by 36

∴ q = 11

- Substitute the value of q in equation (5)

∴ p + 4(11) = 64

∴ p + 44 = 64

- Subtract 44 from both sides

∴ p = 20

- Substitute the value of q in (3)

∴ n = 3(11) = 33

∴ n = 33

<em>There are 20 pennies, 33 nickels and 11 quarters</em>

6 0

2 years ago

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Samantha and Mia each left Julia’s house at the same time. Mia walked north at 7 kilometers per hour. Samantha ran west at 11 ki

Lena [83]

Mia walked 7km/h so after 1 hour, she is 7 km north of the house of Julia

Samantha walked 11km/h so after 1 hour, she is 11 km west of the house of Julia.

The points where Mia and Samantha are after 1 hour , and the house of Julia form a right triangle with sides 7 and 11 km. The distance between the girls, is the hypotenuse of his triangle.

by the pythagorean theorem:

$MS= \sqrt{ 7^{2} + 11^{2} }= \sqrt{49+121}= \sqrt{170}= 13 (km)$

Answer: 13 km

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2 years ago

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Kenny types 280 words. How long did he <br> type for?<br> A.4<br> B. 5<br> C.6<br> D. 7

zlopas [31]

Are you sure you didn’t miss anything while writing the question?

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2 years ago

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The center of a circle is at the origin on a coordinate grid. The vertex of a parabola that opens upward is at (0, 9). If the ci

zhannawk [14.2K]

Answer:

"The maximum number of solutions is one."

Step-by-step explanation:

Hopefully the drawing helps visualize the problem.

The circle has a radius of 9 because the vertex is 9 units above the center of the circle.

The circle the parabola intersect only once and cannot intercept more than once.

The solution is "The maximum number of solutions is one."

Let's see if we can find an algebraic way:

The equation for the circle given as we know from the problem without further analysis is so far $x^2+y^2=r^2$ .

The equation for the parabola without further analysis is $y=ax^2+9$ .

We are going to plug $ax^2+9$ into $x^2+y^2=r^2$ for $y$ .

$x^2+y^2=r^2$

$x^2+(ax^2+9)^2=r^2$

To expand $(ax^2+9)^2$ , I'm going to use the following formula:

$(u+v)^2=u^2+2uv+v^2$ .

$(ax^2+9)^2=a^2x^4+18ax^2+81$ .

$x^2+y^2=r^2$

$x^2+(ax^2+9)^2=r^2$

$x^2+a^2x^4+18ax^2+81=r^2$

So this is a quadratic in terms of $x^2$

Let's put everything to one side.

Subtract $r^2$ on both sides.

$x^2+a^2x^4+18ax^2+81-r^2=0$

Reorder in standard form in terms of x:

$a^2x^4+(18a+1)x^2+(81-r^2)=0$

The discriminant of the left hand side will tell us how many solutions we will have to the equation in terms of $x^2$ .

The discriminant is $B^2-4AC$ .

If you compare our equation to $Au^2+Bu+C$ , you should determine $A=a^2$

$B=(18a+1)$

$C=(81-r^2)$

The discriminant is

$B^2-4AC$

$(18a+1)^2-4(a^2)(81-r^2)$

Multiply the (18a+1)^2 out using the formula I mentioned earlier which was:

$(u+v)^2=u^2+2uv+v^2$

$(324a^2+36a+1)-4a^2(81-r^2)$

Distribute the 4a^2 to the terms in the ( ) next to it:

$324a^2+36a+1-324a^2+4a^2r^2$

$36a+1+4a^2r^2$

We know that $a>0$ because the parabola is open up.

We know that $r>0$ because in order it to be a circle a radius has to exist.

So our discriminat is positive which means we have two solutions for $x^2$ .

But how many do we have for just $x$ .

We have to go further to see.

So the quadratic formula is:

$\frac{-B \pm \sqrt{B^2-4AC}}{2A}$

We already have $B^2-4AC}$

$\frac{-(18a+1) \pm \sqrt{36a+1+4a^2r^2}}{2a^2}$

This is t he solution for $x^2$ .

To find $x$ we must square root both sides.

$x=\pm \sqrt{\frac{-(18a+1) \pm \sqrt{36a+1+4a^2r^2}}{2a^2}}$

So there is only that one real solution (it actually includes 2 because of the plus or minus outside) here for x since the other one is square root of a negative number.

That is,

$x=\pm \sqrt{\frac{-(18a+1) \pm \sqrt{36a+1+4a^2r^2}}{2a^2}}$

means you have:

$x=\pm \sqrt{\frac{-(18a+1)+\sqrt{36a+1+4a^2r^2}}{2a^2}}$

or

$x=\pm \sqrt{\frac{-(18a+1)-\sqrt{36a+1+4a^2r^2}}{2a^2}}$ .

The second one is definitely includes a negative result in the square root.

18a+1 is positive since a is positive so -(18a+1) is negative

2a^2 is positive (a is not 0).

So you have (negative number-positive number)/positive which is a negative since the top is negative and you are dividing by a positive.

We have confirmed are max of one solution algebraically. (It is definitely not 3 solutions.)

If r=9, then there is one solution.

If r>9, then there is two solutions as this shows:

$x=\pm \sqrt{\frac{-(18a+1)+\sqrt{36a+1+4a^2r^2}}{2a^2}}$

r=9 since our circle intersects the parabola at (0,9).

Also if (0,9) is intersection, then

$0^2+9^2=r^2$ which implies r=9.

Plugging in 9 for r we get:

$x=\pm \sqrt{\frac{-(18a+1)+\sqrt{36a+1+4a^2(9)^2}}{2a^2}}$

$x=\pm \sqrt{\frac{-(18a+1)+\sqrt{36a+1+324a^2}}{2a^2}}$

$x=\pm \sqrt{\frac{-(18a+1)+\sqrt{(18a+1)^2}}{2a^2}}$

$x=\pm \sqrt{\frac{-(18a+1)+18a+1}{2a^2}}$

$x=\pm \sqrt{\frac{0}{2a^2}}$

$x=\pm 0$

$x=0$

The equations intersect at x=0. Plugging into $y=ax^2+9$ we do get $y=a(0)^2+9=9$ .

After this confirmation it would be interesting to see what happens with assume algebraically the solution should be (0,9).

This means we should have got x=0.

$0=\frac{-(18a+1)+\sqrt{36a+1+4a^2r^2}}{2a^2}$

A fraction is only 0 when it's top is 0.

$0=-(18a+1)+\sqrt{36a+1+4a^2r^2}$

Add 18a+1 on both sides:

$18a+1=\sqrt{36a+1+4a^2r^2$

Square both sides:

$324a^2+36a+1=36a+1+4a^2r^2$

Subtract 36a and 1 on both sides:

$324a^2=4a^2r^2$

Divide both sides by $4a^2$ :

$81=r^2$

Square root both sides:

$9=r$

The radius is 9 as we stated earlier.

Let's go through the radius choices.

If the radius of the circle with center (0,0) is less than 9 then the circle wouldn't intersect the parabola. So It definitely couldn't be the last two choices.

7 0

2 years ago

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How do u solve -18-6k=6 (1+3k)

Anarel [89]

Let's solve your equation step-by-step.<span><span><span>−18</span>−<span>6k</span></span>=<span>6<span>(<span>1+<span>3k</span></span>)

</span></span></span>Step 1: Simplify both sides of the equation.
<span><span><span>−18</span>−<span>6k</span></span>=<span>6<span>(<span>1+<span>3k</span></span>)
</span></span></span><span>Simplify: (Show steps)</span><span><span><span>−<span>6k</span></span>−18</span>=<span><span>18k</span>+6

</span></span>Step 2: Subtract 18k from both sides.<span><span><span><span>−<span>6k</span></span>−18</span>−<span>18k</span></span>=<span><span><span>18k</span>+6</span>−<span>18k</span></span></span><span><span><span>−<span>24k</span></span>−18</span>=6

</span>Step 3: Add 18 to both sides.<span><span><span><span>−<span>24k</span></span>−18</span>+18</span>=<span>6+18</span></span><span><span>−<span>24k</span></span>=24

</span>Step 4: Divide both sides by -24.<span><span><span>−<span>24k</span></span><span>−24</span></span>=<span>24<span>−24</span></span></span><span>k=<span>−1

</span></span>Answer:<span>k=<span>−<span>1</span></span></span>

5 0

2 years ago

Read 2 more answers