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Kruka [31]
3 years ago
8

a teacher had 21 red pens. if the ratio of red pens to blue pens she owned was 3:1 , how many pens did she have in total

Mathematics
2 answers:
snow_lady [41]3 years ago
8 0
She had 21:7 because if you multiply 3:1 by 7 each it is 21:7 so she had 7 blue pens
erma4kov [3.2K]3 years ago
5 0
There are 21 red pens. For every 3 red pens, there is 1 blue pen.
Let's make these into a fraction equation.
21/p=3/1
p is the number of blue pens we have yet to find.
First, cross multiply.
21x1=21
px3=3p
Now, we have an equation of
21÷3p
We set it equal to 1, and we solve it.
21÷3p = 1
(21÷3p)×3p=1×3p
21=3p
21÷3=(3p)÷3
7=p
So, if there are 21 red pens, there are 7 blue pens.
We add these together to find the total number of pens the teacher has.
21+7=28
The teacher has 28 pens total.
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Answer:

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Step-by-step explanation:

Step 1: Write equation

-2x + 8 = 18

Step 2: Solve for <em>x</em>

  1. Subtract 8 on both sides: -2x = 10
  2. Divide both sides by -2: x = -5

Step 3: Check

<em>Plug in x to verify it's a solution.</em>

-2(-5) + 8 = 18

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1. A cheetah can run at a top velocity of 31 m/s and has a mass of 47 kg. What is the cheetahs kenetic energy?
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1. 22583.5 J

2. 1248 kg

3. 78.09 m/s

Step-by-step explanation:

The formula for kinetic energy is ;

K.E = 1/2* m * v²

Where m is the mass and v is the velocity

1.

K.E = 1/2 * m*v²

K.E = 1/2 * 47 * 31²

K.E = 22583.5 J

2.

Velocity = 9.78 m/s.

Kinetic energy = 60,800 J

To get mass, apply the formula as;

K.E = 1/2 * m*v²

60,800 = 1/2 * m * 9.78²

60800 = 48.70845 m

60800/48.70845 = m

1248 = m

Mass = 1248 kg

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K.E = 143.3 J

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Apply the formula;

K.E = 1/2 * m*v²

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143.3/0.0235 = v²

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