You don't really get that long. The key to these is simply practice as many people are a little rusty. The key thing for me is the patterns and translating things into simple patterns. IE, with the 50 mins one, you wanted an hour, divide by 5 and times by 6. Simple maths is the key, don't overcomplicate, just look for the common theme as in simple maths and you'll crack it. With practice you see the same patterns and it becomes fairly simple.