The students need a 1 to 25 grid (or list).They are then give instructions to shade in different types of numbers such as square numbers, primes, multiple of 4 etc. After shading in all the required numbers they will be left with 4 or 5 unshaded values which they add to get the target number.

This a a mental arithmetic starter with 3 different levels shown on the same slide. A starting number is given and the students work their way down the list performing the operations in order. The second slide shows the answers

Mental arithmetic challenges to project. A start number is given on the first slide followed by 9 or 10 subsequent operations on the following the slides. The aim is for the students to get the correct target number (answer) shown on the final slide. 9 different sets of of differeing levels of difficulty