Questions   
Sort: 
 #1
avatar+2433 
+1

 

A 25 foot ladder leans against a vertical wall. The foot of the ladder is 7 feet from the base of the wall. If the top of the ladder slips 4 feet down the wall, how far will the foot of the ladder slide?      

 

One way to do this is to use Pythagoras' Theorem twice.  Sort of a before and after.    

This would be much better if I could just draw the pictures.  But I can't, so here goes...   

 

Visualize the ladder as the hypotenuse of a right triangle.  

Then the hypotenuse is 25 and the ground side is 7.   

 

By the theorem a2 + b2 = c2, then    a2 (the wall)  =  c2 (the ladder) – b2 (the ground)        

 

                                                         a2  =  252 – 72    

                                                         a2  =  625 – 49  =  576       

                                                         a  =  sqrt(576)  =  24 (the height of the wall side)      

 

When the ladder slips 4 feet down the wall, the new "a" becomes 20   

The hypotenuse stays the same 25 because it's a ladder   

 

So now we can say                         b2 (the ground)  =  252 (the ladder) – 202 (the wall)         

 

                                                       b2  =  625 – 400  =  225    

                                                       b  =  sqrt(225)  =  15 (the length of the ground side)    

 

When the top of the ladder slid down the side of the wall 4 feet,

the bottom of the ladder slid out until it was 15 feet from the wall.   

 

The ladder was already 7 feet from the wall, so the bottom of the ladder slid 8 feet.   

.

Jul 2, 2023
Jul 1, 2023
Jun 30, 2023
 #3
avatar+1166 
+2
Jun 30, 2023
 #1
avatar+2433 
0

 

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  

.

Jun 30, 2023

1 Online Users