Represent Sample Spaces for Compound Events

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7th Grade Math › Represent Sample Spaces for Compound Events

Questions 1 - 10
1

A student flips a coin twice. Which set is the complete sample space for this compound event?

{H, T}

{HH, TT}

{HH, HT, TT}

{HH, HT, TH, TT}

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coin flips {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches for each possibility, like four paths for two flips. For example, for a coin flip and die roll, the list is {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two flips shows branches leading to HH, HT, TH, TT. The correct representation here is choice A, which lists all four possible outcomes for two coin flips. Common errors include omitting TH as in B, listing single flips as in C, or only matching outcomes as in D. When creating a list, systematically combine all outcomes from each flip, such as 2 times 2 equals 4. For identifying events, translate descriptions to locate and count, avoiding incomplete lists or confusing with single events.

2

A student spins a spinner with 4 equal sections labeled A, B, C, D and then flips a coin. How many outcomes are in the complete sample space?

6

8

10

12

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coins {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches, such as for flipping a coin twice yielding 4 paths. For example, a coin flip followed by a die roll has a list {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two coin flips shows paths HH, HT, TH, TT. The correct count here is choice B, 8 outcomes from 4 spinner results times 2 coin flips. Common errors include undercounting like 6 in A or overcounting like 12 in D, perhaps confusing spinner sections. When creating a sample space, multiply independent possibilities: 4 x 2 = 8. To identify the total, list systematically like A-H, A-T, etc.; mistakes often involve wrong multiplication or ignoring one event.

3

Two number cubes labeled 1–6 are rolled. The ordered pair $(a,b)$ means (first cube, second cube). How many outcomes are in the event “the sum is 8”?

4

5

6

8

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coins {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches, such as for flipping a coin twice yielding 4 paths. For example, a coin flip followed by a die roll has a list {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two coin flips shows paths HH, HT, TH, TT. The correct count here is choice B, 5 outcomes where the sum is 8, such as (2,6), (3,5), (4,4), (5,3), (6,2). Common errors include undercounting by missing doubles like (4,4) or overcounting pairs that sum to other values. When creating a table, use rows and columns for each die and mark cells where a + b = 8 to count them. To identify and count, translate 'sum is 8' into pairs and enumerate systematically; mistakes often involve ignoring order or miscounting symmetric pairs.

4

A student flips a coin twice. Using the sample space {HH, HT, TH, TT}, which outcomes match the event “at least one head”?

{HH}

{TT}

{HH, HT, TH}

{HT, TH}

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coin flips {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches for each possibility, like four paths for two flips. For example, for a coin flip and die roll, the list is {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two flips shows branches leading to HH, HT, TH, TT. The correct representation here is choice D, which includes all outcomes with at least one head: HH, HT, TH. Common errors include only both heads as in A, only mixed as in B, or no heads as in C. When creating a list, systematically combine outcomes, then filter for the event like 'at least one'. For identifying events, translate phrases like 'at least' to include all matching, avoiding errors like excluding TH or miscounting.

5

A student draws one colored tile from a bag, does not put it back, and then draws a second tile. The bag contains 2 red tiles (R) and 1 blue tile (B). If outcomes are written in order (first draw, second draw), which list is the complete sample space?

{RR, RB}

{RR, RB, BR}

{RR, RB, BR, BB}

{R, B}

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coin flips {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches for each possibility, like four paths for two flips. For example, for a coin flip and die roll, the list is {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two flips shows branches leading to HH, HT, TH, TT. The correct representation here is choice B, listing all possible outcomes without replacement: RR, RB, BR, excluding impossible BB. Common errors include including BB as in A, single draws as in C, or incomplete like D. When creating a list for without replacement, account for changing possibilities, like after drawing R, options are R or B. For identifying events, consider dependencies and avoid listing impossibles or confusing with replacement.

6

A student rolls two standard six-sided dice. Use an ordered pair $(a,b)$ to mean “die 1 shows $a$, die 2 shows $b$.” Which list correctly gives all outcomes for the event “sum equals 8”?

${(1,7),(2,6),(3,5),(5,3),(6,2),(7,1)}$

${(2,6),(3,5),(4,4),(5,3),(6,2)}$

${(6,2),(6,3),(6,4),(6,5),(6,6)}$

${(2,6),(3,5),(4,4)}$

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possibilities, such as for two coins {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches, such as for flipping twice yielding 4 paths. To identify events, read the description like 'both heads' as HH or 'at least one' as HH, HT, TH, then locate and count them. For example, a coin and die list is {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for flipping twice shows HH, HT, TH, TT. The correct list is choice A, including all pairs summing to 8 like (2,6) to (6,2). Common errors include missing reverses in B, invalid numbers like 7 in C, or only first die 6 in D. When creating a list, systematically combine all possibilities; for tables, use rows and columns; for trees, branch out with paths as outcomes. To identify events, translate the language like 'sum equals', locate matching outcomes, and count them, avoiding mistakes like incomplete lists, ignoring order, wrong counts, or including invalid outcomes.

7

Two different number cubes labeled 1–6 are rolled. Event $F$ is: “Both numbers are odd.” How many outcomes are in $F$?​

3

6

9

12

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coins {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches, such as for flipping a coin twice yielding 4 paths. For example, a coin flip followed by a die roll has a list {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two coin flips shows paths HH, HT, TH, TT. The correct count here is choice C, 9 outcomes where both are odd (3 odds per die: 3x3=9). Common errors include counting only one die's odds in A or overcounting in D. When creating a table, mark cells where both a and b are odd and count them. To identify and count, translate 'both odd' to qualifying pairs; mistakes often involve confusing 'both' with 'at least one' or wrong odd numbers.

8

A student flips a coin and then rolls a number cube labeled 1–6. Which list shows the complete sample space for this compound event (coin result first, then number)?

{H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}

{H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5}

{1H, 2H, 3H, 4H, 5H, 6H, 1T, 2T, 3T, 4T, 5T, 6T, HT, TH}

{H, T, 1, 2, 3, 4, 5, 6}

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coins {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches, such as for flipping a coin twice yielding 4 paths. For example, a coin flip followed by a die roll has a list {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two coin flips shows paths HH, HT, TH, TT. The correct representation here is choice B, which lists all 12 outcomes completely and accurately. Common errors include incomplete lists like missing T6 in choice A, ignoring combinations in choice C, or adding irrelevant outcomes like HT and TH in choice D. When creating a list, systematically combine all possibilities from each event, such as 2 coin outcomes times 6 die outcomes for 12 total. To identify the complete sample space, translate the sequence of events into ordered pairs and ensure all are enumerated without duplicates or omissions; mistakes often involve forgetting outcomes or confusing independent events.

9

A student rolls two standard number cubes. Outcomes are ordered pairs (first roll, second roll). How many outcomes are in the event “the sum is 8”?

4

5

6

36

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possible outcomes, such as for two coin flips {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches for each possibility, like four paths for two flips. For example, for a coin flip and die roll, the list is {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and the event 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for two flips shows branches leading to HH, HT, TH, TT. The correct representation here is choice B, with 5 outcomes where the sum is 8: (2,6), (3,5), (4,4), (5,3), (6,2). Common errors include undercounting to 4 or 6, or listing total outcomes as 36. When creating a table, fill a 6x6 grid and count cells meeting the condition. For identifying events, translate 'sum is 8' and count carefully, avoiding mistakes like ignoring (4,4) or double-counting.

10

A student randomly chooses one shirt (Red or Blue) and then one pair of shorts (Black, Gray, or Tan). How many outcomes are in the sample space?

5

6

8

12

Explanation

This question tests representing compound sample spaces with lists, tables, or trees, identifying outcomes from everyday language descriptions. Representations include lists that enumerate all possibilities, such as for two coins {HH, HT, TH, TT}, tables in a grid like 6×6 for two dice, or trees with branches, such as for flipping twice yielding 4 paths. To identify events, read the description like 'both heads' as HH or 'at least one' as HH, HT, TH, then locate and count them. For example, a coin and die list is {H1, H2, H3, H4, H5, H6, T1, T2, T3, T4, T5, T6}, and 'heads and even' is {H2, H4, H6} with probability 3/12; a tree for flipping twice shows HH, HT, TH, TT. The correct count is 6 in choice B, from 2 shirts times 3 shorts. Common errors include 5 miscounting, 8 adding extras, or 12 doubling. When creating a list, systematically combine all possibilities; for tables, use rows and columns; for trees, branch out with paths as outcomes. To identify events, translate the language for total space, locate all outcomes, and count them, avoiding mistakes like incomplete multiplication, wrong event language, confusing branches, or miscounting combinations.

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