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avatar+2431 
+1

 

I drove to the beach at a rate of 40 miles per hour.  If I had driven at a rate of 50 miles per hour instead, then I would have arrived 45 minutes later.  How many miles did I drive?  

 

You mean 45 minutes earlier.  Obviously, if you drive faster, you get there faster.  

 

This problem makes use of

the following relationship:                   Distance = Velocity x Time 

 

                                                           D  =  V • T  

 

case 1                                                 D  =  (40) • (T)  

 

case 2                                                 D  =  (50) • (T – 45)  

 

Since the Distance, D, is the  

same for both cases, let's set       

the "V•T"s equal to each other.             (50)(T – 45)  =  (40)(T)  

 

                                                               50T – 2250  =  40T  

 

Subtract 40T from both sides                  10T – 2250  =  0  

 

Add 2250 to both sides                                       10T  =  2250  

 

Divide both sides by 10                                           T  =  225   (this is in minutes)  

 

Divide minutes by 60 to get hours                           T  =  225 min / 60 min/hr  =  3.75 hours  

 

Plug this T back into original equation                     D  =  (40 mi/hr) • (3.75 hr)  =  150 miles  

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Jul 12, 2023
 #1
avatar+2431 
+1

 

I have to paint one side of a wall.  The wall is 12 meters tall and 120 meters long.  Each gallon of paint covers 150 square feet. If a foot is approximately 0.3048 meters, then what is the smallest whole number of gallons I can buy and have enough paint to cover the whole wall? 

 

 

We're going to have to convert metric units to imperial units,  

so I think it's better to do it from the start.  Even though we'll  

have fractions to contend with, a calculator makes that easy.  

 

                                                                       12 m  

1 foot is 0.3048 meter, so the height is       –––––––––  =  39.3701 ft   

                                                                   0.3048 m/ft  

 

                                                                       120 m  

1 foot is 0.3048 meter, so the length is       –––––––––  =  393.7007 ft   

                                                                   0.3048 m/ft  

 

Area is height times length     (39.3701 ft)(393.7007 ft)  =  15,500.0359 sq ft  

 

1 gallon will cover 150 sq ft  

so divide that into the area               15,500.0359 sq ft  

                                                        –––––––––––––––  =  103.3335 gallons  

                                                           150 sq ft/gallon  

 

You can't buy just a third of a gallon of paint,  

so we have to round that up to whole gallons                       104 gallons  

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Jul 12, 2023
 #1
avatar+2431 
+1

 

One ordered pair (a,b) satisfies the two equations ab^4 = 48 and ab = 72. What is the value of b in this ordered pair?    

 

 

To find b, consider                                                  ab4  =  48  

 

We will divide both sides by ab.  

 

Since ab=72, we will divide the left side  

by "ab" and the right side by its equal 72.  

                                                                              ab4         48  

                                                                             ——   =   ——  

                                                                              ab           72  

Note that ab4 = (ab) * (b3)  

 

Cancel ab out of the left side.  

Reduce 48/72 on the right side.  

                                                                               b3           2  

                                                                             ——   =   ——  

                                                                                1            3  

 

 

                                                                                 b   =   cube root of (2 / 3)  

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Jul 12, 2023
 #1
avatar+8 
0

To find the possible values of ab, a+b, a, and b, we'll use the given equations and solve them simultaneously.

(a) Finding all possible values of ab:

From the equation a - b = 4, we can rewrite it as a = b + 4.

Substituting this value of a into the equation a^3 - b^3 = 0, we get:
(b + 4)^3 - b^3 = 0

Expanding the equation, we have:
(b^3 + 12b^2 + 48b + 64) - b^3 = 0

Simplifying the equation, we get:
12b^2 + 48b + 64 = 0

Dividing the equation by 4 to simplify it further, we have:
3b^2 + 12b + 16 = 0

Using the quadratic formula, we can solve for b:
b = (-12 ± √(12^2 - 4316))/(2*3)
b = (-12 ± √(144 - 192))/(6)
b = (-12 ± √(-48))/(6)

Since the discriminant is negative, there are no real solutions for b. Therefore, there are no possible real values for ab.

(b) Finding all possible values of a + b:

Given a - b = 4, we can rewrite it as a = b + 4.

Substituting this value of a into the equation a + b, we get:
(b + 4) + b = 2b + 4

So, the possible values of a + b are all real numbers of the form 2b + 4.

(c) Finding all possible values of a and b:

We have a - b = 4. By substituting the value of a from this equation into the equation a + b = 2b + 4, we get:
(b + 4) + b = 2b + 4

Simplifying the equation, we have:
2b + 4 = 2b + 4

This equation is true for all values of b. Therefore, there are infinitely many possible values for a and b that satisfy the given conditions.

In summary:
(a) There are no possible real values for ab.
(b) The possible values of a + b are all real numbers of the form 2b + 4.
(c) There are infinitely many possible values for a and b that satisfy the given conditions.

Jul 12, 2023
Jul 11, 2023

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