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3 years ago

14

Kristina wants to buy a flute that costs 240 . She has saved 20 each week for 3 weeks . How many more weeks does Kristina need t

o save money if she continues to save 20 each week

1 answer:

Burka [1]3 years ago

7 0

Answer:

9 more weeks

Explanation:

She already saved 20(3)=60

240=60+20(x)
X=9
She needs 9 more weeks

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Expand (x-y)^4 “expand each binomial”

soldier1979 [14.2K]

Answer:

(x-y)(x-y)(x-y)(x-y)

Step-by-step explanation:

(x-y)^4 means multiply (x-y) four times

8 0

2 years ago

If 180° < α < 270°, cos⁡ α = −817, 270° < β < 360°, and sin⁡ β = −45, what is cos⁡ (α + β)?

eduard

Answer:

$cos(\alpha+\beta)=-\frac{84}{85}$

Step-by-step explanation:

we know that

$cos(\alpha+\beta)=cos(\alpha)*cos(\beta)-sin(\alpha)*sin(\beta)$

Remember the identity

$cos^{2} (x)+sin^2(x)=1$

step 1

Find the value of $sin(\alpha)$

we have that

The angle alpha lie on the III Quadrant

so

The values of sine and cosine are negative

$cos(\alpha)=-\frac{8}{17}$

Find the value of sine

$cos^{2} (\alpha)+sin^2(\alpha)=1$

substitute

$(-\frac{8}{17})^{2}+sin^2(\alpha)=1$

$sin^2(\alpha)=1-\frac{64}{289}$

$sin^2(\alpha)=\frac{225}{289}$

$sin(\alpha)=-\frac{15}{17}$

step 2

Find the value of $cos(\beta)$

we have that

The angle beta lie on the IV Quadrant

so

The value of the cosine is positive and the value of the sine is negative

$sin(\beta)=-\frac{4}{5}$

Find the value of cosine

$cos^{2} (\beta)+sin^2(\beta)=1$

substitute

$(-\frac{4}{5})^{2}+cos^2(\beta)=1$

$cos^2(\beta)=1-\frac{16}{25}$

$cos^2(\beta)=\frac{9}{25}$

$cos(\beta)=\frac{3}{5}$

step 3

Find cos⁡ (α + β)

$cos(\alpha+\beta)=cos(\alpha)*cos(\beta)-sin(\alpha)*sin(\beta)$

we have

$cos(\alpha)=-\frac{8}{17}$

$sin(\alpha)=-\frac{15}{17}$

$sin(\beta)=-\frac{4}{5}$

$cos(\beta)=\frac{3}{5}$

substitute

$cos(\alpha+\beta)=-\frac{8}{17}*\frac{3}{5}-(-\frac{15}{17})*(-\frac{4}{5})$

$cos(\alpha+\beta)=-\frac{24}{85}-\frac{60}{85}$

$cos(\alpha+\beta)=-\frac{84}{85}$

4 0

3 years ago

What is the vertex of the function in #5

ziro4ka [17]

Where is the function

5 0

3 years ago

50 is 40% of what number??????

kvv77 [185]

So a hack is we know that 20% times 5 =100% and 40 divided by 2=20 so

50=40%
divide both sides by 2
25=20%

20 times 5=100 so
multiply both sides by 5
125=100%

8 0

3 years ago

Read 2 more answers

| 9. The distance between Town A and Town B was 108 km. A car and a van left Town A at 12 00 for Town B. On reaching Town B, the

Westkost [7]

Answer:

a) Time until both vehicles meet is 1.5 hours after starting at noon. That makes it 1:30PM.

b) Average speed of car is 84 km/h

Step-by-step explanation:

A -----------------------z------------B

<u>Left</u> <u>Speed(km/h)</u> <u>Time</u>

Car: 12PM X

Van: 12PM 60

Car/Van

DistanceCar AB + z

DistanceVan Az

Ratio: (AB+z)/Az = 7/5

Time until both meet = T (in hours)

Distance Car: xT

Distance Van: 60T

====

xT = AB + z

60T = Az

---

(xT/60T)= (7/5)

x = 60(7/5)

x = 84 km/h

=====

Time for car to reach B is: time (hr) = 108 km/(84 km/h)

time = 1.286 hours

Distance for at 1.289 hours is: distance (km) = (60 km/h)*(1.286 h)

distance = 77.14 km

At 1.286 hours, the car reverses direction. The van is (108 km - 77.14 km) or 30.86 km away.

Add the distances travelled by both vehicles after the car reverses direction at 1.286 hours. The sum will be 30.86 km when they meet, at time of T.

Car Distance + Van Distance = 30.86 km

T(84 km/h) + t(60 km)

They meet when they are 0 km apart, which can be modeled with the following equation:

Van travel Distance - Car Travel Distance = 0 starting at 1.286 hr.

Let <u>t</u> be the time <u>after</u> 1.286 hours that both vehicles meet/collide.

t*(60 km/h) + t(84 km/h) = 30.86 km

t(60+84) = 30.86 km

t(144 km/h) = 30.86 km

t = 0.2143 hr

Total time until the car and van meet is 1.286 hr + 0.2143 hr for a total of 1.50 hours.

=================

a) Time until both vehicles meet is 1.5 hours after starting at noon. That makes it 1:30PM.

b) Average speed of car is 84 km/h

==============

<u>CHECK</u>

Is the ratio of the distance travelled by the car and the van until they meet in the ratio of 7/5?

Car distance is (1.5 hr)(84 km/h) = 126 km

Van distance is (1.5 hr)(60 km/h) = 90.0 km

Ratio is 126/90 or 1.4

Ratio of 7/5 is 1.4

<u><em>YES</em></u>

3 0

2 years ago