This is simple algebra. Remember when you were little and you had questions like 2 + (Fish, Cat, etc. Sign) =5 What is the fish sign? It is 3 because 5-2=3. In your case, put it into that perspective. 3 + X= 51. 51-3=48. X=48.
reciprocal
102
When one of the numbers is prime and the other is 1.
The product of 18 and 4 is 72
82.62712
reciprocal
The LCM of two numbers is one of the numbers when one of the numbers is a multiple of the other. The LCM of two numbers is the product of the numbers when they are relatively prime. In all other cases (like consecutive even numbers that aren't 2 and 4) the LCM is as you describe.
102
When one of the numbers is prime and the other is 1.
The "product" of two numbers is the answer you get when you multiplyone of them by the other one, in either order.
The product of 18 and 4 is 72
82.62712
More than possible. Unless one of your prime numbers is 2, the product of any other two will be odd.
One is the reciprocal of the other
It is the number one.
You can compare them by looking at them (they are the same)subtracting one from the other (answer = 0)dividing one by the other (the quotient is 1).
When one of them divides evenly into the product with no remainder and the result is the other number.