The difference between 3 times a number and 21

Mathematics

1 answer:

pashok25 [27]3 years ago

7 0

The difference (-) between 3 times a number (3n) and 21.

3n - 21

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When truckers are on long-haul drives, their driving logs must reflect their average speed. Average speed is the total distance

bekas [8.4K]

a) $v=\frac{d_{tot}}{t_{tot}}=\frac{(3 h)(60 mph)+20 mi}{3 h +t_2}$

The average speed is equal to the ratio between the total distance ( $d_{tot}$ and the total time taken ( $t_{tot}$ ):

$v=\frac{d_{tot}}{t_{tot}}$

the distance travelled by the trucker in the first 3 hour can be written as the time multiplied by the velocity:

$d_1 = (3 h)(60 mph)=180 mi$

So the total distance is

$d_{tot}=d_1 +d_2 = 180 mi+20 mi=200 mi$

The total time is equal to the first 3 hours + the time taken to cover the following 20 miles in the city:

$t_{tot}=3 h +t_2$

So, the equation can be rewritten as:

$v=\frac{d_{tot}}{t_{tot}}=\frac{(3 h)(60 mph)+20 mi}{3 h +t_2}$

b) 0.50 h (half a hour)

Since we know the value of the average speed, $v=57.14 mph$ , we can substitute it into the previous equation to find the value of $t_2$ , the time the trucker drove in the city:

$v=\frac{200 mi}{3h +t_2}\\3h+t_2 = \frac{200 mi}{v}\\t_2 = \frac{200 mi}{v}-3h=\frac{200 mi}{57.14 mph}-3 h=0.50 h$

3 0

3 years ago

−4y−4+(−3)<br> i need help solving this

ololo11 [35]

Answer: The answer is negastive 11 although I am not one thousand percent sure that this is the answer, if it is not the correct anser then please tell me and I can get the corecct anwer for you!

4 0

3 years ago

Read 2 more answers

Help meeee with this questionnnnnnnnnn!!!!!!!!!!!!

Dafna1 [17]

Given:

The scale factor between two circles is $\dfrac{2x}{5y}$ .

To find:

The ratio of their areas.

Solution:

We know that, all circles are similar.

The ratio of the areas of similar figures is equal to the ratio of squares of their corresponding sides or equal to the square of ratio of their corresponding sides.

The scale factor is the ratio of the corresponding sides.

Ratio of areas of circles = Square of scale factor between two circles

$\text{Ratio of areas of circles}=\left(\dfrac{2x}{5y}\right)^2$