All categories

3 years ago

Plz help me with this

Mathematics

2 answers:

forsale [732]3 years ago

5 0

Answer:

$\frac{31x}{30}$

Step-by-step explanation:

Before adding we require the fractions to have a common denominator

The lowest common denominator of 2, 5 and 3 is 30, thus

$\frac{15x}{15(2)}$ + $\frac{6x}{6(5)}$ + $\frac{10x}{10(3)}$

= $\frac{15x}{30}$ + $\frac{6x}{30}$ + $\frac{10x}{30}$

Add the numerators leaving the denominator

= $\frac{15x+6x+10x}{30}$ = $\frac{31x}{30}$

wariber [46]3 years ago

3 0

Answer: $\bold{c)\quad \dfrac{31x}{30}}$

<u>Step-by-step explanation:</u>

$\dfrac{x}{2}+\dfrac{x}{5}+\dfrac{x}{3}\\\\\text{The LCD of 2, 5, and 3 is }2\cdot 5\cdot 3=30\\\text{Multiply each term so their denominator is 30:}\\\\\\\dfrac{x}{2}\bigg(\dfrac{15}{15}\bigg)+\dfrac{x}{5}\bigg(\dfrac{6}{6}\bigg)+\dfrac{x}{3}\bigg(\dfrac{10}{10}\bigg)\\\\\\=\dfrac{15x}{30}+\dfrac{6x}{30}+\dfrac{10x}{30}\\\\\\=\dfrac{15x+6x+10x}{30}\\\\\\=\large\boxed{\dfrac{31x}{30}}$

You might be interested in

The function G(x)=f(x+3)+2 which of the following is true of the graph of g(x)?

zepelin [54]

G(x)=(x+3)+2

G(x) = (x-h) + k
h translates the graph left/right and k translates the graph up/down.
Because the equation is x- the parenthesis is (x - - 3) which makes h a negative 3 and will translate left. The k positive so it will move up.
Letter B

7 0

3 years ago

You are a lifeguard and spot a drowning child 60 meters along the shore and 40 meters from the shore to the child. You run along

sukhopar [10]

Answer:

The lifeguard should run across the shore a distance of 48.074 m before jumpng into the water in order to minimize the time to reach the child.

Step-by-step explanation:

This is a problem of optimization.

We have to minimize the time it takes for the lifeguard to reach the child.

The time can be calculated by dividing the distance by the speed for each section.

The distance in the shore and in the water depends on when the lifeguard gets in the water. We use the variable x to model this, as seen in the picture attached.

Then, the distance in the shore is d_b=x and the distance swimming can be calculated using the Pithagorean theorem:

$d_s^2=(60-x)^2+40^2=60^2-120x+x^2+40^2=x^2-120x+5200\\\\d_s=\sqrt{x^2-120x+5200}$

Then, the time (speed divided by distance) is:

$t=d_b/v_b+d_s/v_s\\\\t=x/4+\sqrt{x^2-120x+5200}/1.1$

To optimize this function we have to derive and equal to zero:

$\dfrac{dt}{dx}=\dfrac{1}{4}+\dfrac{1}{1.1}(\dfrac{1}{2})\dfrac{2x-120}{\sqrt{x^2-120x+5200}} \\\\\\\dfrac{dt}{dx}=\dfrac{1}{4} +\dfrac{1}{1.1} \dfrac{x-60}{\sqrt{x^2-120x+5200}} =0\\\\\\ \dfrac{x-60}{\sqrt{x^2-120x+5200}} =\dfrac{1.1}{4}=\dfrac{2}{7}\\\\\\ x-60=\dfrac{2}{7}\sqrt{x^2-120x+5200}\\\\\\(x-60)^2=\dfrac{2^2}{7^2}(x^2-120x+5200)\\\\\\(x-60)^2=\dfrac{4}{49}[(x-60)^2+40^2]\\\\\\(1-4/49)(x-60)^2=4*40^2/49=6400/49\\\\(45/49)(x-60)^2=6400/49\\\\45(x-60)^2=6400\\\\$

$x$

As $d_b=x$ , the lifeguard should run across the shore a distance of 48.074 m before jumpng into the water in order to minimize the time to reach the child.