SME
Grade 3 Science · Problem type
Which fossil is older?
Use this for “Which fossil is older?” from the rock layers.
Diagram
Layers above the fish: 2.
Layers above the shell: 6.
The shell is 4 layers deeper than the fish, so it is older.
This is an example. Type your own values to start a new problem.
Layers above the fish
example
Layers above the shell
example
Layers apart
calculated
Formulas
2 and 6 are 4 apart
Difference between layers above the fish and layers above the shell = layers apart
Assumptions
•
A fossil is what is left of a living thing from long ago, kept in rock.
•
Rock forms in layers, one on top of another. A deeper layer is older.
•
A fossil with more layers above it is older. That holds when the layers have not been turned over.
•
A fish fossil on a mountain shows the place was once under water.
Step-by-step
WE KNOW
Layers above the fish: 2
Layers above the shell: 6
FIND
layers apart
Step 1 · Find layers apart
2 and 6 are ? apart
Difference between layers above the fish and layers above the shell = layers apart
Take the smaller number of layers away from the bigger one.
Layers apart = 6 − 2
Layers apart = 4 (the shell fossil is deeper, so older)
Check
Put the numbers back in. Both sides should match.
6 − 2 = 4 ✓
Topic check
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