No calculator
The maths is easy, the time pressure makes it difficult. 25 questions, 12 minutes. Thats 30 seconds a question. If you don't know the answer move on.
Its all basic maths dressed up in a sentance. a man drills 5 holes in 3 minutes, how many does he drill in a 4 hour morning. tyres are 35 pounds each, you get a 25% discount if you buy 4 - how much do you pay for 4. That sort of stuff. Basic addition, subtraction, multiplication and division only.
Practice, practice, practice mental airthmetic - including learning to do good approximations. what's 19x21 off the top of your head? instantly? nope i dunno either but 19x21 has gotta be bloody close to 20x20 so i'll guess at 400 as the answer - its multiple choice so using those sort of techniques will get you very close to the right answer.
Don't sweat it if you don't finish - very few people do - I'm a self confessed maths geek with 2 degrees in numerate / engineering / mathsy subjects and I didn't finish all 25 questions, but I passed.