Crack The Safe - Types of Number (HCF/LCM)

Two “Crack The Safe” activities on types of numbers and HCF/LCM. The two sheets are split into types of number and HCF/LCM problems. These contain six questions but ten possible answers meaning that students can self-check their answers (are they in the list of possible answers?) whilst the teacher can help those who require it. I use these as starters and plenaries but that is obviously up to you.