Anonymous
Anonymous asked in Education & ReferenceHomework Help · 1 decade ago

Homework help please !?

i need help. you have to write and algebraic model:

A car travels at an average speed of 45 miles per hour for 8 miles, reduces its speed by 15 miles per hour for the next 4 miles, and then returns to a speed of 45 miles per hour. how long does the car travel at the reduced speed. CAN SOMEONE EXPLAIN PLS ?

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  • Carrot
    Lv 5
    1 decade ago
    Favorite Answer

    The car doesn't go 15 miles for the next 4 miles, it reduces its speed by 15 miles, which leaves it at 30 mph.

    30 mph = 30 miles/60 min = 1 mile/ 2 min

    He goes 4 miles, which means that he was traveling at that speed for 8 minutes. (4 miles * 2 min/mile = 8 minutes)

  • 1 decade ago

    We only need the original 45mph from the first part of the question to tell us our original speed. So, when you reduce your speed by 15mph you get

    45mph - 15 mph = 30mph

    The next part I would do as a ratio because it is simpler that way.

    1. Change 1hr to 60 min

    2. Compare 30mi/60min -->this is your rate or speed -- to

    3. Miles driven, 4mi.

    Your ratio will look like:

    30 mi/ 60 min = 4mi/ x min

    1. Cross multiply

    30mi * x min = 60min *4mi

    2. 30x = 240 -- some teachers want the units, some don't

    3. Divide both sides by 30 and ...

    x = 8min

  • olli
    Lv 4
    4 years ago

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