SME
Grade 4 Science · Earth & Space Science
Earth processes: weathering, erosion and rock layers
Use this for “The rocks weighed 120 g before shaking and 95 g after. How much wore away?”
Chart
120
95
Mass worn away: 25 g
This is an example. Type your own values to start a new problem.
Mass before shaking (g)
−
Mass after shaking (g)
=
Mass worn away (g)
Formulas
120 − 95 = 25
Mass before shaking − mass after shaking = mass worn away
Assumptions
•
Weathering breaks rock into smaller pieces. Shaking rocks in a jar is a fast model of it.
•
Weigh the rocks before and after. The pieces knocked off are the mass worn away.
•
Erosion moves the pieces away: water, ice, wind and gravity.
Step-by-step
WE KNOW
Mass before shaking: 120 g
Mass after shaking: 95 g
FIND
mass worn away
Step 1 · Find mass worn away
120 − 95 = ?
Mass before shaking − mass after shaking = mass worn away
Take the mass after shaking away from the mass before.
0
11
10
1
2
0
−
9
5
2
5
Mass worn away = 25 g
Check
Put the numbers back in. Both sides should match.
120 − 95 = 25 ✓
Topic check
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