At roulette, the chance of winning a bet on a single number is 1/38.
a) Write down a numerical expression for the chance of winning between 20 and 35 bets (inclusive) out of 1000 bets on a single number. Do not evaluate this expression.
b) Should the normal curve be used to approximate the chance in a)? (Give a reason.) If yes, find the normal approximation. If no, use some better method of approximation.