Math Problem Statement

Solve using discrete math

a) Construct the truth table for the compound proposition (p → q) ∨ (¬p → q). b) How can the English sentence 'You cannot ride the roller coaster if you are under 4 feet tall unless you are older than 15 years old.' be translated into a logical expression?

Solution

Let's break down and solve the parts of this question using discrete math:

Part (a) Truth Table for (pq)(¬pq)(p \rightarrow q) \lor (\neg p \rightarrow q):

First, recall the basic operations:

  • pqp \rightarrow q is the implication: it is false only if pp is true and qq is false.
  • ¬p\neg p is the negation of pp.
  • \lor represents logical disjunction (OR), which is true if at least one of the propositions is true.

We'll construct the truth table step-by-step:

ppqqpqp \rightarrow q¬p\neg p¬pq\neg p \rightarrow q(pq)(¬pq)(p \rightarrow q) \lor (\neg p \rightarrow q)
TTTFTT
TFFFFF
FTTTTT
FFTTFT
  • Column 3: pqp \rightarrow q is true except when p=Tp = T and q=Fq = F.
  • Column 4: ¬p\neg p is the negation of pp.
  • Column 5: ¬pq\neg p \rightarrow q is true except when ¬p=T\neg p = T and q=Fq = F.
  • Column 6: The disjunction (pq)(¬pq)(p \rightarrow q) \lor (\neg p \rightarrow q) is true whenever either of the previous implications is true.

Part (b) Translation of the English Sentence into a Logical Expression:

The sentence is: “You cannot ride the roller coaster if you are under 4 feet tall unless you are older than 15 years old.”

Let:

  • pp: "You are under 4 feet tall."
  • qq: "You are older than 15 years old."
  • rr: "You can ride the roller coaster."

The sentence can be broken down into two parts:

  1. "You cannot ride the roller coaster if you are under 4 feet tall."

    • This can be written as: p¬rp \rightarrow \neg r (If you are under 4 feet tall, you cannot ride).
  2. "Unless you are older than 15 years old."

    • "Unless" translates to "if not." So, this can be written as ¬q¬r\neg q \rightarrow \neg r (If you are not older than 15, you cannot ride).

Thus, the full logical expression becomes: (p¬r)(¬q¬r)(p \rightarrow \neg r) \land (\neg q \rightarrow \neg r) This means you cannot ride the roller coaster if either you are under 4 feet tall or not older than 15.


Let me know if you would like further details!

Here are five related questions you can explore:

  1. What is the truth table for pqp \lor q (disjunction of pp and qq)?
  2. How does De Morgan’s Law apply to this proposition?
  3. Can the logical expression in part (b) be simplified using any identities?
  4. What is the equivalent of pqp \rightarrow q using only conjunctions and negations?
  5. How would the truth table change if we replaced \lor with \land in part (a)?

Tip: Logical equivalences like De Morgan's Laws are key tools for simplifying complex propositions.

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Math Problem Analysis

Mathematical Concepts

Propositional Logic
Truth Tables
Logical Equivalence

Formulas

p → q
¬p
p ∨ q

Theorems

Properties of Implication
Logical Equivalence

Suitable Grade Level

Grades 11-12