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Searching & Sorting

Eleventh graders learn how computers find data fast with binary search — repeatedly halving a sorted list — a classic efficient algorithm that beats checking every item one by one.

Grade 11Algorithms55 minutes1 class periodUse → Modify → CreateExplicit teaching4 StandardsCSTA
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Lesson at a Glance

Everything you need before the bell rings

Learning Objectives

Students will be able to…

  • ✓Explain binary search.
  • ✓See why sorting helps.
  • ✓Order the steps.
  • ✓Search efficiently.
Essential Question

How does a computer find one name among a million, in an instant? A clever algorithm: binary search. How does it work?

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Lesson Phases
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Vocabulary Terms
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Standards Aligned
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Interactive Task
Put in Order · Interactive

Order the Binary Search Steps

Project this and have students put the binary search steps in order.

🔍 Put the binary search steps in order!Try it
Tap the first step!
The Lesson · Use → Modify → Create (a coding progression with Unplugged practice)

55 minutes, five moves

Tap any phase to open the teacher moves and student actions.

1

Hook — Find One in a Million

6 min

How does a computer find one name in a million instantly? Binary search!

👩‍🏫 Teacher Moves

  • Play a number-guessing game.
  • Ask the best strategy.
  • Set up.

🎒 Student Actions

  • Play.
  • Strategize.
  • Get ready.
2

Unplugged — Unplug It

11 min

Students practice.

👩‍🏫 Teacher Moves

  • Guess a number 1–100.
  • Always guess the middle.
  • Count the steps.

🎒 Student Actions

  • Guess.
  • Halve it.
  • Count.
3

Use — Order the Steps

16 min

Students use.

👩‍🏫 Teacher Moves

  • Send students to Order the Binary Search Steps.
  • Order them.
  • Note the sorted list.

🎒 Student Actions

  • Order.
  • Note it.
  • Explain.
4

Modify — Modify

13 min

Students modify.

👩‍🏫 Teacher Moves

  • Trace a search on a list.
  • Count the comparisons.
  • Compare to linear search.

🎒 Student Actions

  • Trace it.
  • Count.
  • Compare.
5

Create — Create

9 min

Students create.

👩‍🏫 Teacher Moves

  • Describe binary search in code.
  • Explain its speed.
  • Complete the exit ticket.

🎒 Student Actions

  • Describe.
  • Explain.
  • Complete the exit ticket.
Standards Alignment

Built to the standards you report on

Aligned to the CSTA K-12 Computer Science Standards (Level 3) and ISTE Standards.

CSTA
3B-AP-11

Analyze searching and sorting.

CSTA
3A-AP-15

Evaluate algorithm efficiency.

CSTA
3A-AP-16

Design algorithms.

ISTE
5

Computational Thinker.

Differentiation

One lesson, every learner

Multilingual Learners

ELL / EMERGING READERS
  • Binary-search step cards.
  • Sentence frame: “First ___, then ___.”
  • Play the guessing game.

Support & Access

IEP / 504
  • Start with the guessing game.
  • Order two at a time.
  • Use a small list.

Stretch & Extend

GIFTED / EARLY FINISHERS
  • Compare to linear search.
  • Explain Big-O.
  • Trace a sort algorithm.
Materials

What to gather

  • 📽️Projector / board
  • 🔢A number line
  • 💻Order the Binary Search Steps
  • 📄A sorted list
  • ✏️Pens
  • 🎫Exit-ticket slips
Vocabulary

Key terms — hover for a quick definition

binary searchhalving a sorted list to find datalinear searchchecking each item in ordersortedin orderalgorithma step-by-step methodefficiencydoing it with less workcomparisonchecking two valuesindexan item’s positionsortto put in order
Evaluate

Exit Ticket

Preview the three formative checks. Tap “Sample answer” to see what mastery looks like — hide them before you print for students.

QUESTION 1
What do you need BEFORE a binary search?
A sorted list.
QUESTION 2
What do you check first in binary search?
The middle item.
QUESTION 3
Why is binary search fast?
It halves the list each step instead of checking every item.

Create: search smart.

Have students play a number-guessing game using binary search (always guess the middle). A printable search sheet is in the Computer Science library.

Study · Flashcards

Study the key terms

Tap a card to flip it, then rate whether you knew it. Built from this lesson’s vocabulary.

🃏 Searching & SortingFlip
Card 1
Term
Tap to flip →
Meaning
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Nice work!

Practice · Quiz

Check your understanding

A quick self-check with instant feedback, drawn from this lesson’s key terms.

📝 Searching & SortingQuiz
Score: 0
1 / 6
Question 1
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Nice work!

Practice · Worksheet

Printable worksheet

A print-and-go review sheet with a built-in answer key. Tap “Show answer key” to reveal answers, or print the clean version for students.

🖨️ Searching & SortingPrint
Name: ________________________
Date: ____________

Part A · Write the word that matches each meaning

Word bank: algorithm, binary search, comparison, efficiency, index, linear search, sort, sorted
  1. to put in order
  2. an item’s position
  3. doing it with less work
  4. a step-by-step method
  5. checking two values
  6. halving a sorted list to find data
  7. checking each item in order
  8. in order

Part B · Show what you learned

  1. What do you need BEFORE a binary search?
  2. What do you check first in binary search?
  3. Why is binary search fast?
Answer key — Part A: 1) sort · 2) index · 3) efficiency · 4) algorithm · 5) comparison · 6) binary search · 7) linear search · 8) sorted
Part B: 1) A sorted list. 2) The middle item. 3) It halves the list each step instead of checking every item.