7th grade math help?

Question

how do i find the least common multiple of 5 and 11

Answer 1

The answer is 55, but your question says that you want to know HOW to do this.

Dave's method works, but it could take a long time if you're working with large numbers.

If you're able to be a bit more sophisticated, you can save some time by applying this method:

1. Find the prime factors of each of the numbers. Remember that you need to consider not only which prime numbers are factors of the numbers, but also HOW MANY TIMES each prime number is used. For example, 2 is the only prime factor of 8, but it occurs 3 times, so the correct prime factors of 8 are 2, 2, 2.

2. Make a list of the prime factors you will need in the least common multiple (LCM). This list includes every prime factor for one of the two numbers you started with, and also every prime factor that occurs in the second number but not the first. Importantly, if a factor occurs in the second number MORE TIMES than it occurs in the first, you have to include it in your LCM that many times.

Example:
Find the LCM of 168 and 180.
Prime factors of 168: 2, 2, 2, 3, 7
Prime factors of 180: 2, 2, 3, 3, 5

Prime factors of LCM: 2, 2, 2, 3, 3, 5, 7

Explanation: 2, 2, 2, 3, 7 are all the prime factors of 168.
We then need another 3 (the factors of 180 include a second 3) and a 5 (since 180 had a 5, which 168 did not).

Answer 2

Write this down on a seperate piece of paper. Start with 5 x 1= , 5 x 2= , 5 x 3= , and so on, up to the highest number in the question (in this case 11). Then do the same with 11 x 1= ,
11 x 2= , 11 x 3= ,,,and so on.
Go down thru both lists and the first number that matches in each column is the least common multiple. In this case, it is 55.
With larger numbers, it's often easier to do them in your head, otherwise you'll use a whole lot of scratch paper.
Let's say 200 and 500. First start by dropping both 0's, now it's just 2 and 5...that's easy...10. Now add the 0's back on...1000 is the least common multiple. 300 and 600....3 and 6....3 will go into 6 really quick on the chart...the LCM is 600.

Answer 3

You look at the prime factors of each number first of all.

However, 5 is prime and 11 is prime, so their only factors are 5 and 11.

The least common multiple is the multiple of all the prime factors, or 5*11 = 55, in this case.

I'll give you an example with non prime numbers, in case it will help you understand:

What is the LCM of 6 and 15?
6 = 2*3
15 = 3*5
Therefore the LCM = 2*3*5 (you get the 2*3 from 6, and the 5 from 15; you don't need the 3 from 15 since you already got the 3 from 6).
So the LCM of 6 and 15 = 2*3*5 = 30

Hope that example helped.

ANSWER (for 5 and 11): 55

Answer 4

Multiply 5 * 11

Answer 5

it is not glaring to evaluate 3/8 and a pair of/3, yet seem at it this way: might you extremely slice a pie into 3 products and take 2 (2/3 of a pie), or slice it into 8 products and take 3 (3/8 of a pie)? in case you like pie, you will probable make the 1st decision, and that's by using fact 2/3 is larger than 3/8. consequently 3/8 < 2/3. the maths thank you to do this's to multiply the left sides by potential of three/3 and the desirable side by potential of 8/8 (the two are fancy approaches of writing a million). then you definately've 9/24 on the left side and sixteen/24 on the desirable side. Now the extensive type on the backside is an identical and it is lots greater basic to evaluate; of course 9/24 < sixteen/24. In different words, you're reducing the pie into 24 products; 3/8 of the pie is comparable to taking 9 products, and a pair of/3 of the pie is comparable to taking sixteen products.

Answer 6

Start with 11 and multiply it by 2, then three, then four, etc., until you find a number that is divisible by 5.

Answer 7

Find all the multiples up to 10 (usually) and then find the least. aka multiply by one then 2 than 3 and so on

Answer 8

okay it is pretty easy, i am in 7th to all u have to do is multiply 5 and 11. Most the time that works, i usually get it rite!

Answer 9

55