Scale Detectives Station Activity
Math Station #3
Scale Detectives: Equality Lab
Grade 2 • Mid-Module Prep
Station Mission:
The equal sign = does NOT mean "write the answer." It means both sides have the same value! Use base-ten blocks or counters to test each case card.
Left Side = Right Side
Balanced = True • Tilted = False
Station Task Cards (Draw a card, solve on your recording sheet)
Cut along dashed lines or keep as a reference board
CASE 01 Misconception Alert
Does this scale balance?
23 − 14 = 14 + 23
Detective Clue: Check both operations carefully. Does subtracting give the same amount as adding?
CASE 02 Check Equality
Does this scale balance?
18 + 7 = 25
Detective Clue: Solve the left side. Compare your answer to the right side number.
CASE 03 Check Equality
Does this scale balance?
30 − 12 = 10 + 8
Detective Clue: Calculate each side first. Are both sides equal to 18?
CASE 04 Balance Equation
Find the missing mystery number:
15 + 9 = 20 + ?
Detective Clue: 15 + 9 has a total value of 24. What plus 20 makes 24?
CASE 05 Check Equality
Does this scale balance?
42 − 15 = 42 − 10
Detective Clue: If you start with 42, does taking away 15 leave the same as taking away 10?
CASE 06 Balance Equation
Find the missing mystery number:
26 − 8 = ? + 10
Detective Clue: What is 26 minus 8? Make the right side have that exact same sum!
Manipulatives available: pan balance, base-ten rods & units, two-color counters Turn to Page 2 for Detective Log
Detective Log: Equality Lab
Show your math thinking to prove whether each case balances or tilts!
Name:
Date:
Part 1: Case Examinations
Calculate left and right sides, then circle your verdict.
CASE 01 23 − 14 = 14 + 23
Left Pan Value: 23 − 14 =
Right Pan Value: 14 + 23 =
Verdict:
BALANCED (True) TILTED (False)
CASE 02 18 + 7 = 25
Left Pan Value: 18 + 7 =
Right Pan Value: 25 =
Verdict:
BALANCED (True) TILTED (False)
CASE 03 30 − 12 = 10 + 8
Left Pan Value: 30 − 12 =
Right Pan Value: 10 + 8 =
Verdict:
BALANCED (True) TILTED (False)
CASE 04 15 + 9 = 20 + ___
Left Side Total: 15 + 9 =
Make Right Side Equal: 20 + ___ = target
Mystery Number:
Missing =
Part 2: The Mystery Fix-It Challenge! (Case 01 Investigation)
A student wrote: 23 − 14 = 14 + 23 because they saw the same numbers.
1. Explain why this scale is TILTED (not equal):
2. Fix it! Change one side so both sides are balanced:
=
Write your new balanced equation
Part 3: Create a Mystery Scale for a Partner
Partner Check
Write an equation with an unknown box (make both sides equal):
Left Expression
=
Right Expression
Partner Signature:
Scale Tested & Balanced!
Station Self-Check: I can test if both sides are equal I know = means the same amount
2nd Grade Math Assessment Prep
