what is the LCM of 4 and 7?

4 = 2 x 2
7 = ...........7
------------------------
...= 2 x 2 x 7
...= 28

28

To find the LCM of any 2 numbers, you have to find the prime factors of each of the numbers first.
4 = 2 * 2 = 2^2
7 = 7^1

Then for each occurring prime factor, take the one from whatever number it has the highest exponent and multiply them.
In this example, the LCM of 4 and 7 is 2^2 * 7^1 = 28

Another example to make it a bit clearer:

We want to calculate the LCM of 18 and 60
18 = 2 * 9 = 2^1 * 3^2
60 = 4 * 15 = 4 * 3 * 5 = 2^2 * 3^1 * 5^1
For primefactor 2, 2^2 is highest occurrence
For primefactor 3, 3^2 is highest occurrence
For primefactor 5, 5^1 is highest occurrence

So the LCM is 2^2 * 3^2 * 5^1 = 4 * 9 * 5 =180

LCM of 4 and 7 :-

4=2*2
7=1*7

therefore, LCM =2*2*1*7=28

4 times 7. you get 28

4 can be decomposed as 2*2
7 is a prime

so having no primes in common in 4 and 7 The LCM is their product 4*7=28

4*7 = 28

28