Question

Sally sells 100 raffle tickets numbered 1 to 100. ( Use "less than one in two","one in two" or "more than one in two" to describe the probability of each of these events happening.)...... a. The winning ticket is a multiple of 5.   b.The winning ticket is an even number.

Answer 1

a. What are the multiples of 5 in the range 1-100? We have 5, 10, 15, 20, ..., 95, 100. To find out how many there are we divide these numbers by 5 to get 1, 2, 3, 4, ..., 19, 20. So it’s obvious there are 20 of them. So we have 20 chances out of 100 which is 20/100=1/5 or “one in five”.

b. The even numbers are 2, 4, 6, .., 100. Divide these by 2: 1, 2, 3, ..., 50. So it’s obvious there are 50 of them. So we have 50 chances out of 100 which is 50/100=1/2 or “one in two”.