SME
Grade 4 Science · Problem type
Grass on a slope
Use this for “How does grass keep soil from washing away?”
Diagram
Soil washed off the bare tray: 320 g.
Soil washed off the grass tray: 60 g.
More washed off the bare tray: 260 g.
This is an example. Type your own values to start a new problem.
Soil washed off the bare tray (g)
−
Soil washed off the grass tray (g)
=
Soil the grass saved (g)
Formulas
320 − 60 = 260
Soil washed off the bare tray − soil washed off the grass tray = soil the grass saved
Assumptions
•
Two trays of soil sit on the same slope. One has grass growing in it.
•
Pour the same water on each. The soil that washes off collects in the jar below.
•
Weigh the soil in each jar. Grass roots hold the soil, so less washes away.
Step-by-step
WE KNOW
Soil washed off the bare tray: 320 g
Soil washed off the grass tray: 60 g
FIND
soil the grass saved
Step 1 · Find soil the grass saved
320 − 60 = ?
Soil washed off the bare tray − soil washed off the grass tray = soil the grass saved
Take the grass tray’s soil from the bare tray’s. That is the soil the grass saved.
2
12
3
2
0
−
6
0
2
6
0
Soil the grass saved = 260 g
Check
Put the numbers back in. Both sides should match.
320 − 60 = 260 ✓
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