**BOLD**, and my answer in

*italics*:

Ok, these problems are "greatest common factor" and "least common multiple" problems.

learn about greatest common factor here:

http://www.math.com/school/subject1/lessons/S1U3L2DP.html

and "least common multiple" here:

http://www.math.com/school/subject1/lessons/S1U3L3DP.html

Least common multiple is the smallest number that a set of numbers can be divided by

In order to learn GCF and LCM, you need to first learn how to do "prime factorization"

learn about that here:

http://www.mathsisfun.com/prime-factorization.html

so, for:

"three salesmen make trips at regular intervals, The first every 7 days, the second every"

15 days and the third 21 days. If they leave the office on the same day for the first trip,

how many days will elapse before they again leave on the same day?

We need to get the least common multiple. we start by finding the prime factors of all 3 numbers:

7: 7

15: 3 X 5

21: 3 X 7

so we have a 3, a 5, and a 7. We multiply them 3X5X7 and get 105. We check our work by seeing if

105 is divisible by 7, 15, and 21. it is.

for:

"Brian is arranging his tanzas in rows. If he puts 11 in a row, there is 1 extra. If he puts 9"

in a row, there is non left. What is the smallest number of tanzas that will alow him to do this?

I don't understand this question. it says "If he puts 11 in a row, there is 1 extra" which makes me

think there is a total of 12, but then that doesn't make sense with 9 and "none left"

for:

"the product of 2 numbers is 2,700 their greatest common factor is 15 what is their least common multiple"

I'm completely stumped