SME
Grade 5 Science · Problem type
How much of Earth’s water is fresh
Use this for “How much of Earth’s water is fresh, and how much is frozen?”
Chart
970 + 20 + 10 = 1,000 liters.
This is an example. Type your own values to start a new problem.
All the water
example · liters
Salt water
calculated · liters
Fresh water
worked out (not typed) · liters
Frozen fresh water
calculated · liters
Liquid fresh water
calculated · liters
Formulas
1,000 × 97 ÷ 100 = 970
All the water × 97 ÷ 100 = salt water
1,000 − 970 = 30
All the water − salt water = fresh water
30 × 2 ÷ 3 = 20
Fresh water × 2 ÷ 3 = frozen fresh water
30 − 20 = 10
Fresh water − frozen fresh water = liquid fresh water
Assumptions
•
About 97 of every 100 liters of Earth’s water are salty ocean water.
•
About 2 of every 3 liters of fresh water are frozen in ice at the poles and on mountains.
•
Most liquid fresh water is under the ground. Lakes and rivers hold very little.
•
Picture all of Earth’s water shrunk to 100, 1,000 or 10,000 liters.
Step-by-step
WE KNOW
All the water: 1,000 liters
FIND
salt water, fresh water, frozen fresh water, liquid fresh water
Step 1 · Find salt water
1,000 × 97 ÷ 100 = ?
All the water × 97 ÷ 100 = salt water
Find how many hundreds, then take 97 for each hundred.
1,000 ÷ 100 = 10
10 × 97 = 970
Salt water = 970 liters
Step 2 · Find fresh water
1,000 − 970 = ?
All the water − salt water = fresh water
The water that is not salty is fresh.
0
9
10
1
0
0
0
−
9
7
0
3
0
Fresh water = 30 liters
Step 3 · Find frozen fresh water
30 × 2 ÷ 3 = ?
Fresh water × 2 ÷ 3 = frozen fresh water
About 2 of every 3 liters of fresh water are frozen.
30 ÷ 3 = 10
10 × 2 = 20
Frozen fresh water = 20 liters
Step 4 · Find liquid fresh water
30 − 20 = ?
Fresh water − frozen fresh water = liquid fresh water
The fresh water that is not frozen is liquid.
Liquid fresh water = 10 liters
Check
Put the numbers back in. Both sides should match.
1,000 × 97 ÷ 100 = 970 ✓
1,000 − 970 = 30 ✓
30 × 2 ÷ 3 = 20 ✓
30 − 20 = 10 ✓
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Earth systems: geosphere, hydrosphere, atmosphere, biosphere
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Water moving through the spheres
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