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aliina [53]
1 year ago
13

Three students have started a fence-painting business. Working together, Pragnesh and Qazi can paint the fence in 12 hours. Simi

larly, Pragnesh and Ronghui can paint the fence in 15 hours when they work together. Finally, when Qazi and Ronghui work together, they can paint the fence in 20 hours. How many hours would it take if all three students worked together to paint the fence?
Mathematics
1 answer:
Mila [183]1 year ago
3 0

Step-by-step explanation:

P and Q can do the whole work in 12 hours.

so, in 1 hour they can do 1/12.

P and R can do in 1 hour 1/15.

Q and R can do in 1 hour 1/20.

mathematically that looks like

P + Q = 1/12

P + R = 1/15

Q + R = 1/20

P + Q + R = 1/x

together they can do 1/x of the work in 1 hour.

it will take them x hours, if all 3 worked together.

from the first equation we get

P = 1/12 - Q

that gives us in the second equation

1/12 - Q + R = 1/15

R = 1/15 - 1/12 + Q = 4/60 - 5/60 + Q = Q - 1/60

but from the 3rd equation we get also

R = 1/20 - Q

so,

Q - 1/60 = 1/20 - Q

2Q = 1/20 + 1/60 = 3/60 + 1/60 = 4/60

Q = 2/60 = 1/30

R = Q - 1/60 = 2/60 - 1/60 = 1/60

P = 1/12 - Q = 1/12 - 2/60 = 5/60 - 2/60 = 3/60 = 1/20

so, we get for the sum :

P + Q + R = 3/60 + 2/60 + 1/60 = 6/60 = 1/10

that means in 1 hour they can do together 1/10 of the work.

so, together they will need 10 hours to paint the fence.

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Step-by-step explanation:

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3 years ago
Add 78, 139, and 14, and then divide by 44.
denpristay [2]

Answer:

5.24, 21/4, or 5 and 1/4

Step-by-step explanation:

78+139+14 = 231

231/44 = 5.25

Or 21/4 (improper fraction)

Or 5 and 1/4 (mixed number)

I'm not exactly sure what you were asking I hope that helps!

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2 years ago
Layla reads 2/5 of her book on Saturday and the other 90 pages to finish the book on Sunday how many pages does Layla's book hav
PolarNik [594]
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5 0
3 years ago
Try to fill in the missing numbers
GrogVix [38]

9514 1404 393

Answer:

  [[274][895][136]]

Step-by-step explanation:

Starting with the middle row, we need a product of two single-digit numbers that is between 53-1 = 52 and 53-9 = 44. Possible products are 5×9=45 and 6×8=48. This means the number in the middle position in the left column must be 8 or 5.

The middle number in the left column cannot be 5, because we must be able to get -5 by subtracting that number from a sum that is at least 3 = 1+2. So, the middle number in the left column is 8, the other two numbers in that column are 1 and 2, and the other two numbers in the middle row are 5 and 9.

There is no product of single-digit numbers that is 30-1 = 29, so the upper left number must be 2, and the bottom left number must be 1. The other two numbers on the top row must be 4 and 7, so that row's equation is 2+4×7=30.

The only remaining digits are 3 and 6. In order to have -3 on the bottom row, the equation there must be 1×3-6 = -3. Then the middle digit must be divisible by 3, so must be 9.

Our solution is ...

row 1: 2 + 7 × 4 = 30

row 2: 8 + 9 × 5 = 53

row 3: 1 × 3 - 6 = -3

And that makes the column equations be ...

col 1: 2 - 8 + 1 = -5

col 2: 7 + 9 / 3 = 10

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6 0
3 years ago
HELP!!!! I WILL GIVE BRAINLIEST TO THE FIRST ANSWER!!!!!!!
aleksklad [387]
I would say c. I’m not sure if I’m right if I’m not sorry but good luck
3 0
3 years ago
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