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2 years ago

2. Find the value of the expression 21 – 2a if a = 3.

Mathematics

2 answers:

timama [110]2 years ago

7 0

Answer:

Step-by-step explanation:

we just substitute the value of "a" given in the above expression we get

21-2(3)

21-6=15

poizon [28]2 years ago

6 0

Answer:

a. 15

Explanation:

Step 1 - Input the value of 'a' in the expression.

21 - 2a

21 - 2(3)

Step 2 - Multiply two and three

21 - 2(3)

21 - 6

Step 3 - Subtract six from twenty one

21 - 6

Therefore, the value of the expression 21 - 2a if a = 3 is a. 15.

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The runner has to race for 21km. She has to finish race before 1h 40min. What avarage speed She has to run to gain such goal?

abruzzese [7]

Answer:

The rate of the runner is 3.5 meters per second.

Step-by-step explanation:

To get this answer in meters per second, we first have to convert each of the terms into either meters or seconds. We can do that by multiplying by unit rates.

21 km * 1000 = 21,000 meters

1 hour * 3600 = 3,600 seconds

40 minutes * 60 = 2,400 seconds

Now we divide the meters by the total number of seconds to get the rate.

21,000 meters / (3,600 + 2,400) secs

21,000 meters / 6,000 secs

3.5 meters per second.

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2 years ago

Suppose compact fluorescent light bulbs last, on average, 11,500 hours. The distribution is normal and the standard deviation is

juin [17]

Answer:

2.275%

Step-by-step explanation:

The first thing to do here is to calculate the z-score

Mathematically;

z-score = (x-mean)/SD

from the question, x = 12,300 hours , mean = 11,500 hours while Standard deviation(SD) = 400 hours

Plugging the values we have;

z-score = (12,300-11,500)/400 = 800/400 = 2

Now, we want to calculate P(z ≤ 2)

This is so because we are calculating within a particular value

To calculate this, we use the z-score table.

Mathematically;

P(z ≤ 2) = 1 - P(z > 2) = 1 - 0.97725 = 0.02275

To percentage = 2.275%

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2 years ago

The teachers sold 32 tickets this is 80% of the tickets given to the teachers how many tickets were given to the teachers

UkoKoshka [18]

You would give the teacher 40 tickets

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2 years ago

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Two ropes are attached to a large ballon in a parade. The people holding the ropes are 40 feet apart,and the angle between the t

qaws [65]

Ropes are 9.63 meters ans 8.178 meters.

Step-by-step explanation:

Step 1 :

List all the given things

Distance between people holding ropes = 40 =(40*0.3048) meters = 12.192 meters

Angle between two ropes = 86 degrees

Angle of elevation of one rope = 42 degrees

Step 2 :

Two angles of triangle are already given so third angle can be calculated as -

Third angle = 180 - ( 86 + 42 ) = 52 degrees

Step 3 :

As we know all three angles we will apply sine rule now, which is

$\frac{a}{sine A} = \frac{b}{sine B} = \frac{c}{sine C}$

Step 4 :

By putting values, we have

$\frac{a}{sine 52} = \frac{b}{sine 42} = \frac{12.192}{sine 86}$

Step 5 : Calculating a and b

$a = 12.192 * \frac{sine 52}{sine 86}$ , $b = 12.192 * \frac{sine 42}{sine 86}$

Step 6 :

By putting values of all sine and calculating we get,

a = 9.63 meters and b = 8.178 meters

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2 years ago

You are required to choose two topics from a list of five to write about on your science test. How many different pairings are p

marissa [1.9K]

A B C D E represent the subjects

A+A1

A+B2

A+C3

A+D4

A+E5

B+B6

B+C7

B+D8

B+E9

C+C10

C+D11

C+E12

D+D13

D+E14

E+E15

15 combos

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2 years ago

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