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Algorithms & Efficiency

Tenth graders learn that some algorithms are far more efficient than others — comparing a slow linear search to a fast binary search — and why efficiency matters as data grows to millions of items.

Grade 10Algorithms50 minutes1 class periodUse → Modify → CreateExplicit teaching4 StandardsCSTA
Start the Lesson
Lesson at a Glance

Everything you need before the bell rings

Learning Objectives

Students will be able to…

  • ✓Compare algorithms.
  • ✓Explain binary search.
  • ✓Order the search steps.
  • ✓Value efficiency.
Essential Question

To find a name in a phone book, you don’t check every page — you jump to the middle and narrow down. That’s a faster algorithm! Why does the efficiency of an algorithm matter so much?

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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

Project this and have students put the steps of a binary search in order — the fast way to find a value in a sorted list.

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

50 minutes, five moves

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

1

Hook — The Phone Book Trick

5 min

You don’t check every page to find a name — you narrow down. Why is that faster?

👩‍🏫 Teacher Moves

  • Pose the search problem.
  • Contrast slow vs. fast.
  • Set the goal.

🎒 Student Actions

  • Consider.
  • Compare.
  • Predict.
2

Unplugged — Unplug It

11 min

Students practice.

👩‍🏫 Teacher Moves

  • Do a linear search by hand.
  • Do a binary search by hand.
  • Count the steps.

🎒 Student Actions

  • Search it.
  • Halve it.
  • Count steps.
3

Use — Order the Search

14 min

Students use.

👩‍🏫 Teacher Moves

  • Send students to Order the Binary Search.
  • Order the steps.
  • Note efficiency.

🎒 Student Actions

  • Order.
  • Note it.
  • Explain.
4

Modify — Compare It

14 min

Students modify.

👩‍🏫 Teacher Moves

  • Compare steps for a big list.
  • Explain why binary wins.
  • Note the sorted requirement.

🎒 Student Actions

  • Compare.
  • Explain.
  • Note it.
5

Create — Create

6 min

Students conclude.

👩‍🏫 Teacher Moves

  • Describe an efficient algorithm.
  • Explain efficiency.
  • Complete the exit ticket.

🎒 Student Actions

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

Built to the standards you report on

Aligned to the CSTA K-12 Computer Science Standards and ISTE Standards for Students.

CSTA
3A-AP-15

Evaluate algorithms for correctness and efficiency.

CSTA
3A-AP-14

Use algorithms to solve problems.

CSTA
3A-AP-13

Create programs that implement algorithms.

ISTE
5

Computational Thinker.

Differentiation

One lesson, every learner

Multilingual Learners

ELL / EMERGING READERS
  • Search-step cards.
  • Sentence frame: “First ___, then ___.”
  • Search with number cards.

Support & Access

IEP / 504
  • Start with linear search.
  • Use a small sorted list.
  • Order two at a time.

Stretch & Extend

GIFTED / EARLY FINISHERS
  • Compare search step counts.
  • Explain Big-O informally.
  • Compare sorting algorithms.
Materials

What to gather

  • 📽️Projector / board
  • 🔢Sorted number cards
  • 💻Order the Binary Search
  • 📋Step handouts
  • ✏️Pens
  • 🎫Exit-ticket slips
Vocabulary

Key terms — hover for a quick definition

algorithma step-by-step problem-solving methodefficiencyhow few steps/resources an algorithm needslinear searchchecking items one by onebinary searchhalving a sorted list each stepsortedarranged in orderinput sizehow much data there isoptimizeto make more efficienttrade-offa balance between costs and benefits
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
Why is binary search faster than linear search?
It cuts the list in half each step instead of checking every item one by one.
QUESTION 2
What must be true about a list to use binary search?
It must be sorted.
QUESTION 3
Why does efficiency matter as data grows?
Slow algorithms become impossibly slow with millions of items; efficient ones stay fast.

Create: an efficient approach.

Have students describe a real search task and explain whether a linear or binary approach would be more efficient. A printable algorithms 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.

🃏 Algorithms & EfficiencyFlip
Card 1
Term
Tap to flip →
Meaning
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Practice · Quiz

Check your understanding

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

📝 Algorithms & EfficiencyQuiz
Score: 0
1 / 6
Question 1
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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.

🖨️ Algorithms & EfficiencyPrint
Name: ________________________
Date: ____________

Part A · Write the word that matches each meaning

Word bank: algorithm, binary search, efficiency, input size, linear search, optimize, sorted, trade-off
  1. how much data there is
  2. a step-by-step problem-solving method
  3. arranged in order
  4. halving a sorted list each step
  5. a balance between costs and benefits
  6. to make more efficient
  7. checking items one by one
  8. how few steps/resources an algorithm needs

Part B · Show what you learned

  1. Why is binary search faster than linear search?
  2. What must be true about a list to use binary search?
  3. Why does efficiency matter as data grows?
Answer key — Part A: 1) input size · 2) algorithm · 3) sorted · 4) binary search · 5) trade-off · 6) optimize · 7) linear search · 8) efficiency
Part B: 1) It cuts the list in half each step instead of checking every item one by one. 2) It must be sorted. 3) Slow algorithms become impossibly slow with millions of items; efficient ones stay fast.