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Posted by **Lilly** on Friday, October 29, 2010 at 2:15am.

- math -
**jai**, Friday, October 29, 2010 at 2:19amrecall that speed or rate is distance traveled over time, or:

speed, v = d/t

thus, you compare Anna's speed and Julia's speed:

Anna: v = 20/(1 1/3)

Julia: v = 246/(16)

*note: first convert mixed number to improper fraction before dividing.

hope this helps. :)

- math -
**Lilly**, Friday, October 29, 2010 at 2:31amso it would e 20/4 over 3? I don't get how I would divide that from 246/16

- math -
**jai**, Friday, October 29, 2010 at 2:38amit's 20/(4/3),, first simplify this,,

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**Lilly**, Friday, October 29, 2010 at 2:46amhow do you simifly that?

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**jai**, Friday, October 29, 2010 at 2:48amwhen dividing a number by a fraction, first get the reciprocal of the fraction,,

*to get reciprocal: you just interchange the numerator and denominator, thus:

reciprocal of 4/3 = 3/4

now the operation becomes multiplication instead of division:

20 * (3/4)

i think you know how to do this. :)

let me see your work.

- math -
**Lilly**, Friday, October 29, 2010 at 2:53amwhich is 12? Then do I divide 12 and 246/16?

- math -
**jai**, Friday, October 29, 2010 at 2:57amnope, it's not 12,,

remember that a whole number can be written to:

20 = 20/1

now,

20/1 * 3/4 = ?

..and we will not divide the answer by 246/16,, we will just compare them.

first, let me see your answer.

- math -
**Lilly**, Friday, October 29, 2010 at 3:01amWell 20 times 3 is 60

1 times 4 is 4

60/4

- math -
**jai**, Friday, October 29, 2010 at 3:05amyou're on the right track,,

now, what is 60/4 ?

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**Lilly**, Friday, October 29, 2010 at 3:07am15/1

- math -
**jai**, Friday, October 29, 2010 at 3:11amright~! :)

now, we simplify 246/16,,

since the numerator and denominator have a common factor 2, we can cancel it out:

(2*123)/(2*8) = 123/8

123/8 is in simplest form,, now change this to mixed number.

- math -
**Lilly**, Friday, October 29, 2010 at 3:25am15 3/8

- math -
**jai**, Friday, October 29, 2010 at 3:32amyes, that's right~! :)

now comparing the speed:

Anna: 15

Julia: 15 3/8

which of the two is slower (or has smaller speed)?

then, "by how much" means you will get the difference:

15 3/8 - 15 = ?

- math -
**Lilly**, Friday, October 29, 2010 at 3:52am3/8

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**jai**, Friday, October 29, 2010 at 3:55amnope,, 15 3/8 is greater than 15,,

it's like you have 15 whole pizza plus 3 slices, while the other has only 15 whole pizzas, that's why,

15 3/8 > 15

then, "by how much" means you will get the difference:

15 3/8 - 15 = ?

- math -
**jai**, Friday, October 29, 2010 at 4:01amoh, i see you already have an answer,,

right. the difference is 3/8 m/s. :)