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3 years ago

Simplify the following expressions.

Mathematics

1 answer:

baherus [9]3 years ago

8 0

1. 36x + 4
2. 30n + 42
3. -24p + 32
4. 24p -28
5. 15m - 30
6. 5x + 45

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a sales person works 3 days per week. she earns 1/3 of her pay on monday and 1/4 on tuesday. how much of her pay does she earn o

kipiarov [429]

First, we have to add the fractions.

1/3 + 1/4 = 7/12

12 - 7 = 5

She earns 5/12 of her paycheck on Wednesday

5 0

3 years ago

Read 2 more answers

A tank contains 60 kg of salt and 1000 L of water. Pure water enters a tank at the rate 6 L/min. The solution is mixed and drain

MissTica

Answer:

(a) 60 kg; (b) 21.6 kg; (c) 0 kg/L

Step-by-step explanation:

(a) Initial amount of salt in tank

The tank initially contains 60 kg of salt.

(b) Amount of salt after 4.5 h

$\text{Let A = mass of salt after t min}\\\text{and }r_{i} = \text{rate of salt coming into tank}\\\text{and }r_{0} =\text{rate of salt going out of tank}$

(i) Set up an expression for the rate of change of salt concentration.

$\dfrac{\text{d}A}{\text{d}t} = r_{i} - r_{o}\\\\\text{The fresh water is entering with no salt, so}\\ r_{i} = 0\\r_{o} = \dfrac{\text{3 L}}{\text{1 min}} \times \dfrac {A\text{ kg}}{\text{1000 L}} =\dfrac{3A}{1000}\text{ kg/min}\\\\\dfrac{\text{d}A}{\text{d}t} = -0.003A \text{ kg/min}$

(ii) Integrate the expression

$\dfrac{\text{d}A}{\text{d}t} = -0.003A\\\\\dfrac{\text{d}A}{A} = -0.003\text{d}t\\\\\int \dfrac{\text{d}A}{A} = -\int 0.003\text{d}t\\\\\ln A = -0.003t + C$

(iii) Find the constant of integration

$\ln A = -0.003t + C\\\text{At t = 0, A = 60 kg/1000 L = 0.060 kg/L} \\\ln (0.060) = -0.003\times0 + C\\C = \ln(0.060)$

(iv) Solve for A as a function of time.

$\text{The integrated rate expression is}\\\ln A = -0.003t + \ln(0.060)\\\text{Solve for } A\\A = 0.060e^{-0.003t}$

(v) Calculate the amount of salt after 4.5 h

a. Convert hours to minutes

$\text{Time} = \text{4.5 h} \times \dfrac{\text{60 min}}{\text{1h}} = \text{270 min}$

b.Calculate the concentration

$A = 0.060e^{-0.003t} = 0.060e^{-0.003\times270} = 0.060e^{-0.81} = 0.060 \times 0.445 = \text{0.0267 kg/L}$

c. Calculate the volume

The tank has been filling at 6 L/min and draining at 3 L/min, so it is filling at a net rate of 3 L/min.

The volume added in 4.5 h is

$\text{Volume added} = \text{270 min} \times \dfrac{\text{3 L}}{\text{1 min}} = \text{810 L}$

Total volume in tank = 1000 L + 810 L = 1810 L

d. Calculate the mass of salt in the tank

$\text{Mass of salt in tank } = \text{1810 L} \times \dfrac{\text{0.0267 kg}}{\text{1 L}} = \textbf{21.6 kg}$

(c) Concentration at infinite time

$\text{As t $\longrightarrow \, -\infty,\, e^{-\infty} \longrightarrow \, 0$, so A $\longrightarrow \, 0$.}$

This makes sense, because the salt is continuously being flushed out by the fresh water coming in.

The graph below shows how the concentration of salt varies with time.

3 0

3 years ago

You roll two dice. What is the probability that the average of the high and low roll is exactly 3, to four decimal places?

Sladkaya [172]

Answer:

0.1111

Step-by-step explanation:

Given that you roll two dice.

the average of the high and low roll is exactly 3,

Since die can show only 1 to 6 we can say average can be 3 in each of the following case.

(1,5) (2,4) (3,3) (4,2) (5,1)

There cannot be any other combination to get average of 3.

Thus favourable events = 4

Sample space will have

(1,1)...(1,6)

(2,1)....

(6,1)...(6,6) i.e. 36

So probability that the average of the high and low roll is exactly 3

= $\frac{4}{36} \\=0.1111$

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3 years ago

Please Help!!!!!! You have twice as many nickels as pennies. you have $1.10. how many of each coin do you have? Solve each probl

astraxan [27]

There are 20 nickels and 10 pennies.

20 cents x 5 is $1.00 and 10 cents x 1 is 10 cents so it is $1.10 because a nickel is 5 cents so 20x5 is a dollar and a penny is worth 1 cent and 10 pennies is 10 cents so $1.00+$0.10=$1.10 brainliest is appreciated! :)

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3 years ago

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kaheart [24]

Answer:

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2 years ago