Video: Using Theoretical Probability to Solve a Word Problem

At a school fair, 68 people entered a raffle. Given that the probability of a girl winning the raffle is 1/4 and people can only enter once, how many girls took part in the raffle?

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Video Transcript

At a school fair, 68 people entered a raffle. Given that the probability of a girl winning the raffle is one-quarter and people can only enter once, how many girls took part in the raffle?

We are told in the question that 68 people entered the raffle and that they can only enter once. This means that 68 tickets were sold in total. We are also told that the probability of a girl winning is one-quarter. This means that one-quarter of the tickets were bought by girls. To work out the number of girls that took part in the raffle, we need to calculate one-quarter of 68. The word “of” in mathematics means multiply or times, so we need to multiply one-quarter by 68.

Multiplying by a quarter is the same as dividing by four, so we can divide 68 by four. Six divided by four is equal to one remainder two, and 28 divided by four is seven. 68 divided by four is therefore equal to 17. We can therefore conclude that 17 girls took part in the raffle.

An alternative method to find a quarter of a number would be to halve it and then halve it again. One-half of 68 is 34, and one-half of this is 17.

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