The probability of one outcome

Difficulty Standard · Set p7vtmn

Give each probability as a fraction in its lowest terms.

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1
A bag holds 1 black counter and 8 blue ones. One is taken without looking. What is the probability that it is black?
2
A bag holds 4 blue counters and 9 green ones. One is taken without looking. What is the probability that it is blue?
3
A bag holds 4 green counters and 1 black one. One is taken without looking. What is the probability that it is green?
4
A bag holds 3 green counters and 8 blue ones. One is taken without looking. What is the probability that it is green?
5
A bag holds 4 black counters and 7 red ones. One is taken without looking. What is the probability that it is black?
6
A bag holds 3 green counters and 1 yellow one. One is taken without looking. What is the probability that it is green?
7
A bag holds 6 green counters and 9 yellow ones. One is taken without looking. What is the probability that it is green?
8
A bag holds 4 yellow counters and 9 red ones. One is taken without looking. What is the probability that it is yellow?
9
A bag holds 6 blue counters and 4 green ones. One is taken without looking. What is the probability that it is blue?
10
A bag holds 6 green counters and 7 red ones. One is taken without looking. What is the probability that it is green?
11
A bag holds 1 red counter and 7 green ones. One is taken without looking. What is the probability that it is red?
12
A bag holds 3 yellow counters and 3 blue ones. One is taken without looking. What is the probability that it is yellow?
13
A bag holds 5 yellow counters and 7 red ones. One is taken without looking. What is the probability that it is yellow?
14
A bag holds 6 black counters and 4 yellow ones. One is taken without looking. What is the probability that it is black?
15
A bag holds 5 green counters and 9 yellow ones. One is taken without looking. What is the probability that it is green?
16
A bag holds 4 yellow counters and 2 red ones. One is taken without looking. What is the probability that it is yellow?
17
A bag holds 9 red counters and 4 yellow ones. One is taken without looking. What is the probability that it is red?
18
A bag holds 3 green counters and 8 red ones. One is taken without looking. What is the probability that it is green?
19
A bag holds 1 yellow counter and 4 green ones. One is taken without looking. What is the probability that it is yellow?
20
A bag holds 5 red counters and 6 yellow ones. One is taken without looking. What is the probability that it is red?

What is in this set

The numbers in this set run from 1 to 9.
A careful solution takes 2 written steps on average.
The mistake this set invites most often, in 100% of the problems: 7 is the rest of the bag, not the whole of it.
Answers are a fraction in its lowest terms, written like 3/4.

Drawing 240 problems from this page produced 225 different ones, 94% — so a sheet of 20 is a new sheet almost every time.

The same skill, harder or easier

We would put this in front of a grade 6 class. That is our judgement, not a standard, and it is printed here so you can disagree with it. Everything else we put in that year.

Next to this

The probability it does not happen

Numbers 1–9; every one will ask for the outcome that does not happen.

How many of them to expect

Numbers 1–120.

All of probability

5 skills in this topic, 15 sets between them.

Printing it

The printed sheet carries no menus and no advertising, and the answer key is on its own page.