The sum of two prime numbers is 21. What is the product of the two numbers?

Question

Please show all of your work. Thanks!

Answer 1

Hi Sophie--

 

First, make a list of all the primes up to 21. (A prime number is one whose only factors are itself and 1. For example, 5 is a prime number because the only numbers you can divide it by are 5 and 1)

 

Once you have your list, grab pairs of them and see if they add up to 21. (There is only one pair that will work.)

 

Once you find that pair, multiply them together.

 

You got this!

 

Matt in NY

Answer 2

                         HI sophie..just as Matt says ...make a list of all the prime numbers

to 21.    2, 3 5 7 11, 13, 17 19   ...Now look at the numbers..which TWO NUMBERS add

up to 21....which are 2 and 19...2 plus 19 =21.....now multiply 2 and 19....

and your ANSWER IS    38....  iTS LIKE SAYING .."What two numbers when added will

give you 21 and when multiplied will give you 38.  Hope you understand...ask again if you wish.