Who is asking: Student
Level: Middle

Question:
One of my math exercises asks:

" Use pairs of prime numbers to find all the numbers less than 50 that have only two prime factors. Make an organized list."

I understand prime and composites but just don't understand this question. Please help. Thank you.

Nikolas

Hi Nikolas,

I started a list of primes to see what they can be. I got

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

The next smallest prime is 29 and the smallest product of 29 with another prime is 229 which is larger than 50.

Start with 2.

What products of 2 with one other prime give a number less than 50?

23, 25, 27, 211, 213, 217, 219, 223

What product of two 2's with one other prime give a number less than 50?

223, 225, 227, 2211

What product of three 2's with one other prime give a number less than 50?

2223, 2225

What product of four 2's with one other prime give a number less than 50?

22223

This is the entire list of numbers less than 50 that have two prime factors, one of which is 2.

Next try 3.

What products of 3 with one other prime larger than 3 give a number less than 50?

35, ...

Can you complete the list?

Penny

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