Yalda has six $5 notes, ten $10 notes and four $20 notes in her purse. If she takes out one note, what is the probability that it will be:
A) a $20 note
B) a $5 or $10 note
C) a $50 note
D) she buys a new toaster with a $20 note and a $10 note. If she now took out a note, what is the probability that it would be a $10 note?
A) # $20 notes/total notes = ?
B) Either-or probabilities are found by adding the individual probabilities.
C) # $50 notes/total = ?
D) 9/18 = ?
To find the probabilities, we need to know the total number of notes Yalda has in her purse. Let's calculate it:
Number of $5 notes = 6
Number of $10 notes = 10
Number of $20 notes = 4
Total number of notes = Number of $5 notes + Number of $10 notes + Number of $20 notes
= 6 + 10 + 4
= 20
Now let's find the probabilities:
A) Probability of selecting a $20 note:
Number of $20 notes / Total number of notes = 4 / 20 = 1 / 5
B) Probability of selecting a $5 or $10 note:
Number of $5 notes + Number of $10 notes / Total number of notes = (6 + 10) / 20 = 16 / 20 = 4 / 5
C) Probability of selecting a $50 note:
As there are no $50 notes mentioned, the probability is 0.
D) After buying the toaster, Yalda has one less $20 note and one less $10 note. Let's update the counts:
Number of $20 notes = 4 - 1 = 3
Number of $10 notes = 10 - 1 = 9
Total number of notes = Number of $5 notes + Number of $10 notes + Number of $20 notes
= 6 + 9 + 3
= 18
Now let's find the probability of selecting a $10 note:
Probability of selecting a $10 note:
Number of $10 notes / Total number of notes = 9 / 18 = 1 / 2
So the probability of selecting a $10 note after buying the toaster is 1/2.