Praxis Core Math

Question

How many even integers greater than 2 and less than 20 are equal in value to the sum of 2 prime numbers? Answer: 8

 

I got this wrong on the practice exam. but how in the world would I begin to figure this out? I'm not sure I even understand what the question is asking.

 

Here is how I approached solving the problem...

 

Step 1: write out all even integers greater than 2 but less than 20

 

4, 6, 8, 10, 12, 14, 16, 18 (there happens to be 8 integers here)

 

Step 2: write out first 10 prime numbers

 

2, 3, 5, 7, 11, 13, 17, 19, 23, 29

 

What is the question asking? And how do I find the solution? Can someone paraphrase the question for me?

Answer 1

You are so totally on the correct track. One more step!

 

3 + 5 (sum of two primes) = 8 (an even number)

3 + 7 = 10

3 + 11 = 14

3 + 13 = 16

3 + 15 = 18

5 + 11 = 16

5 + 13 = 18

7 + 11 = 18

 

And there are you 8 pairs.

Answer 2

can you find any two numbers in List 2 (from step 2) totaling 18?    5+ 13

...totaling 16?    3 + 13

...totaling 14?    3 + 11

...totaling 12?    5 + 7

...totaling 10?    3 + 7

...totaling 8?      3 + 5

...totaling 6?

...totaling 4?     

 

Check this analysis.