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Strike441 [17]
3 years ago
7

Sally can paint a room in 5 hours while it takes Steve 3 hours. How long would it take them to paint if they worked together

Mathematics
2 answers:
Stella [2.4K]3 years ago
6 0
It would be 8 hours because you are adding 5 and 3 to get a total
diamong [38]3 years ago
5 0

Answer: it will take them 1.875 hours to paint if they worked together

Step-by-step explanation:

Sally can paint a room in 5 hours. This means that in 1 hour, 1/5 of the room. Her unit rate is 1/5

Steve 3 hours to paint the same room. It means that his unit rate per hour is 1/3

If they work together, it would take a lesser time because they would be working simultaneously and at their individual rates. It means that their rates are additive. Their combined individual rate will be 1/5 + 1/3

Assuming they worked together and finished the painting in t hours, their combined rate per hour will be 1/t. Therefore

1/5 + 1/3 = 1/t

3 + 5/15 = 1/t

8/15 = 1/t

8t =15

t = 15/8 = 1.875 hours

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"A rectangle has a height of 5 cm and its base is increasing at a rate" of 3/2 cm/min. When its area is 60 cm2, at what rate is
sukhopar [10]

Answer:

The diagonal is increasing at the rate of 119/104cm/min of the given rectangle.

Step-by-step explanation:

Dimensions of the rectangle

Height = 5cm

Rate of base = 3/2 cm/min

Area = 60cm^2

We know the area of a rectangle of given by = base* Height

b*h = 60

b*5 = 60

b = 12cm

Applying Pythagoras theorem while drawing a diagonal to the rectangle

  b^2 +h^2 =  D^2\\

 5^2 +12^2 = 13^2

so our diagonal will be 13cm  

Upon differentiating the area of the rectangle  we get

b*h = A=60cm^2

using  the chain rule of differentiation

h*db/dt + b*dh/dt  = 0

b*dh/dt = -h*db/dt

12*dh/dt = -5*3/2

dh/dt = -5/8 cm//min

so the height of the rectangle is decreasing at the rate of -5/8cm/min

now we have all the measurements we need

b = 12 , db/dt = 3/2cm/min

h = 5 , dh/dt = -5/8 cm/min

b^2 +h^2  = D^2

Upon differentiating we get

2b*db/dt + 2h*dh/dt = 2D*dD/dt

b*db/dt + h*dh/dt = D*dD/dt

12*3/2 + 5*(-5/8) = 13*dD/dt

18 -25/8 = 13*dD/dt

\frac{144-25}{8} = 13*dD/dt

dD/dt = \frac{119}{104} cm/min

Therefore the diagonal is increasing at the rate of 119/104cm/min of the given rectangle.

6 0
3 years ago
If stamps are $0.30 how many stamps can Janice buy with $7.20
snow_lady [41]
Divide the total amount of money Janice has by the cost of the stamps.

$7.20 / $0.30 = 24

Janice can buy 24 stamps.
7 0
3 years ago
PLEASE HURRY ITS A TEST
AnnyKZ [126]
8+5+8=21 coins in total.
8/21*7/20=
56/420=
2/15. Hope this helps, and PM me if something's not clear!
4 0
3 years ago
To make rice, you mix 1.5 cups of water for every 1 cup of dry rice. This will make 2 servings. How many cups of dry rice and ho
dalvyx [7]

Answer:

7.5 cups of water

5 cups of dry rice

Step-by-step explanation:

In total 1.5 water and 1 cup rice will equal 2 servings. If you are serving 10 people, you need to multiply each by 5.

6 0
3 years ago
Can some one helppppppppppp
alexdok [17]

Answer:

66 ft

Step-by-step explanation:

L ∝ n

L = kn , k -> number of sections

Length of 3 sections=  18 ft

3n = 18

 n = 18/3

n = 6 ft

Length of 1 section of fence = 6 ft

Length of 11 sections of fence = 6* 11 = 66 ft

5 0
3 years ago
Read 2 more answers
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