SOLUTION: Hello I couldn't find the section up here for models or scales but i had a some questions about this topic and I thank anyone who can help me.The first question is, A toy airplane

Question 71879: Hello I couldn't find the section up here for models or scales but i had a some questions about this topic and I thank anyone who can help me.The first question is, A toy airplane is 10 inches long.If the actual airplane is 75 feet long,find the scale of the model.The next one is,An N-gauge train model is created using a scale of 1:160 ft.If an actual train engine,the K-4,an early twentieth-century engine,is 45 feet long,what is the length of an N-gauge model of the engine in inches.The third one is,The actual distance from Fargo,ND to Minneapolis,MN is 240 miles.If the scale on a map is 1 inch=20 miles,how long is a line on the map connecting the two cities.And the last one is,a bag contains 7 red marbles,3 blue marbles,and 6 green marbles.You choose a marble at random.What are the odds of choosing a green marble. Thank you for anyone that helps me
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
These problems can be solved by using ratios. The first one is simply a ratio of 75 to 10 which can be written as 75:10. However it needs to be reduced, so it could be rewritten as 15:2, since each has a factor of 5.

The second one can be written as
Where x is the length of the scale model.
So the scale model is 9/32 feet or 3.375 inches

The 3rd problem can be expressed as
Where x is the length of the line on the map
We need to convert everything to inches, so the units match up. Multiply the denominator on the left and right by (5280*12). This converts from miles to inches.
Solve for x
Even though these numbers look nasty, they divide to get 12(there are decimal roundoffs that I forgot to put in). So the length of the line is 12 inches. This makes sense because if 1 inch is 20 miles, then 12 inches is 240 miles (12*20=240)

For the last one, the odds of choosing a green marble are the number of green marbles over the total number of marbles

                           # of green
                 P(green)= ------------
                             # total

                                6
                 P(green)= ------------
                               6+7+3

                                6
                 P(green)= ------------
                                16

                                3
                 P(green)= ------------
                                8

P(green)=3/8
So the chances of picking a green marble are 3 of 8 or a 37.5% chance
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