Question

Four students are running for class president: liz, sam, sue, and tom. the probabilities of sam, sue, and tom winning are 7⁄25 , 3⁄10 and 21⁄100 , respectively. what is the probability of liz winning?

Answer 1

First, we need to convert all the fractions to have the same denominator. 10 and 25 are both multiples of 100, so 100 would be appropriate. 

Sam has a 7/25 chance. Because we want ?/100, something needs to change. To get from 25 to 100, you need to times 25 by 4, right? So, do the same with the 7.
7 x 4 = 28. Therefore Sam has a 28/100 chance.

Sue has 3/10. Using the same method, we can see that 3 needs to be multiplied by 10 (because 10 times 10 = 100). So Sue has a 30/100 chance.

Tom is already in the fraction we like, so just keep this as 21/100. 

Now, add 28/100, 30/100 and 21/100 to get 79/100. 

Because won of them will get the role of class president, we know that the probability adds to 1. To get a full probability (100/100, or 1), what needs to be added to 79/100? 

Another way of going about this is 100/100-79/100. The answer is 21/100

The probability of Liz winning is 21/100. 

Let me know if this is still unclear, I would be more than happy to explain in more detail if necessary :) 

Answer 2

Considering that the sum of the probabilities has to be 1 = 100%, it is found that there is a 0.21 = 21% probability of liz winning.

The probabilities are:

• $\frac{7}{25}$ for Sam.
• $\frac{3}{10}$ for Sue.
• $\frac{21}{100}$ for Tom.
• x for Liz.

The sum is 1 = 100%, thus

$\frac{7}{25} + \frac{3}{10} + \frac{21}{100} + x = 1$

Then

$\frac{28 + 30 + 21 + 100x}{100} = 1$

$79 + 100x = 100$

$100x = 21$

$x = \frac{21}{100}$

$x = 0.21$

0.21 = 21% probability of liz winning.

A similar problem is given at https://brainly.com/question/3480028