Solve equation - 4=x/20-5

The cost of 3 large candles and 5 small candles is $6.40. the cost of 4 large candles and 6 small candles is $7.50. which pair o

cricket20 [7]

T = large candles and s = small candles

3t + 5s = 6.40
4t + 6s = 7.50

^^ this would be ur system of equations

8 0

3 years ago

Read 2 more answers

Tim must read 2 books from a list of 7 recommended books for his summer reading program. In how many different ways can Tim choo

Marianna [84]

There are 21 ways Tim choose 2 books from the 7 recommended book

Solution:

Given that Tim must read 2 books from a list of 7 recommended books for his summer reading program

To find: different ways can Tim choose 2 books from the 7 recommended books

This is a combination problem

A combination is a selection of all or part of a set of objects, without regard to the order in which objects are selected

The formula for combinations is:

$n C_{r}=\frac{n !}{r !(n-r) !}$

where n represents the number of items, and r represents the number of items being chosen at a time

Here we have to choose 2 books from 7 books

Therefore, n = 7 and r = 2

Substituting values in above formula, we get

$\begin{aligned}&7 C_{2}=\frac{7 !}{2 !(7-2) !}\\\\&7 C_{2}=\frac{7 !}{2 ! \times 5 !}\end{aligned}$

For a number n, the factorial of n can be written as,

$n !=n \times(n-1) \times(n-2) \dots \dots \times 2 \times 1$

Therefore, we get

$7 C_{2}=\frac{7 \times 6 \times 5 \times 4 \times 3 \times 2 \times 1}{2 \times 1 \times 5 \times 4 \times 3 \times 2 \times 1}\\\\7C_2 = 7 \times 3 = 21$

Thus there are 21 ways Tim choose 2 books from the 7 recommended book

7 0

3 years ago

The school orchestra has 20 woodwinds, 20 brass instruments, 45 percussionists and 15 strings. Select the portion of the instrum

Alona [7]

Find total instruments:

20+20+45+15 = 100

20 are brass

The portion would be number of brass over total:

20/100 which reduces to 1/5 are brass

6 0

3 years ago

Read 2 more answers

an electrition charged $70 for 2 hours of work and 115 for 5hours of work write an equtionto find the cost for y and xk

Westkost [7]

$\bf \begin{array}{ccll} \stackrel{x}{hours}&\stackrel{y}{cost}\\ \cline{1-2} 2&70\\ 5&115 \end{array}~\hspace{10em}(\stackrel{x_1}{2}~,~\stackrel{y_1}{70})\qquad (\stackrel{x_2}{5}~,~\stackrel{y_2}{115}) \\\\\\ slope = m\implies \cfrac{\stackrel{rise}{ y_2- y_1}}{\stackrel{run}{ x_2- x_1}}\implies \cfrac{115-70}{5-2}\implies \cfrac{45}{3}\implies 15$

$\bf \begin{array}{|c|ll} \cline{1-1} \textit{point-slope form}\\ \cline{1-1} \\ y-y_1=m(x-x_1) \\\\ \cline{1-1} \end{array}\implies y-70=15(x-2)\implies y-70=15x-30 \\\\\\ y=15x+40\impliedby \begin{array}{|c|ll} \cline{1-1} slope-intercept~form\\ \cline{1-1} \\ y=\underset{y-intercept}{\stackrel{slope\qquad }{\stackrel{\downarrow }{m}x+\underset{\uparrow }{b}}} \\\\ \cline{1-1} \end{array}$

as you already know, a direct proportional variation has a constant of variation "k", y = kx, which in this case that'd be the slope, namely 15.

7 0

3 years ago

The mean length of the sides of a triangular plot of land is 18 yards.

Sunny_sXe [5.5K]

The mean is all of them added together divided by the number, so multiple the mean by the number of sides, 3, and that's the perimeter. 18 x 3 = 54

8 0

3 years ago