A reservoir starts with 100 units, receives 30 and loses 20 over the period. Find its ending stock.
Answer and explanation
110
100+30−20=110.
Subjects
Systems accounting
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Sample exercises
Which is a flow unit?
- A calendar date
- Tonnes only
- Metres only
- Tonnes per year
Answer and explanation
Tonnes per year
A flow measures transfer per time.
Why state a system boundary?
- It makes uncertainty disappear
- It guarantees zero emissions
- It determines which inputs, outputs and processes are counted
- It replaces all measurements
Answer and explanation
It determines which inputs, outputs and processes are counted
Accounting depends on inclusion rules.
A constant flow of 4 units/day continues for 7 days. Find transferred amount.
Answer and explanation
28 units
4×7=28.
Why can an improvement inside one boundary increase a burden elsewhere?
Answer and explanation
A process may shift energy, materials or emissions to another location or stage. A broader assessment can reveal the tradeoff.
Credit burden shifting.
Does an uncertain estimate become exact when shown with many decimal places?
- No
- Yes, always
- Only in a long report
- Only in a spreadsheet
Answer and explanation
No
Displayed precision is not measurement accuracy.
Study notes
Environmental stocks, flows and system boundaries
A stock is an amount present at a time; a flow is an amount transferred per time. Mixing their units can produce invalid comparisons.
Grades 9–12Environmental stocks, flows and system boundaries · revision notes
A stock is an amount present at a time; a flow is an amount transferred per time. Mixing their units can produce invalid comparisons.
Grades 9–12