21 brain games guaranteed to boost your brain power
Your brain isn’t a muscle – in fact, it’s mostly fat – but the right kind of mental exercise can help keep it in shape. These puzzles are designed to give your problem-solving, reasoning, and concentration skills a workout. And they come in varying degrees of difficulty, so pace yourself!
How many times does the digit 5 occur in the numbers from 1 to 100?
Twenty times. The digit 5 appears 10 times as a last digit (5, 15, 25 … 95) and 10 times as a first digit (50, 51, 52 … 59).