Calculator -- why? It's a simple division of 240 divided by 5. To divide by 5, divide by 10 and multiply by 2 to get 48. Then the 0.001 in the denominator gives you 48 kΩ.
Well geeeeeeee I know that but I was trying to get him to work it out himself. I could have given him the answer as well. Having taught electronics for years I found that if the students are give the answers they never learn. If they work it out themselves it sticks in. I hope that doesn't sound like I am having a go at you because I am not. Just trying to help people help themselves out there.
PS. If he is under 25 and from the Australian school system he probably won't know how to work it out without a calculator. I have a 9yo son who has had a calculator at school since grade 2. Sucks. As a parent I got into trouble for not letting him take it to school.