SME
Grade 12 Science · Problem type
How long a reserve lasts
Use this for “400 billion barrels of oil are used at 12.5 billion a year. How many years will they last?”
Diagram
Each slice of the bar is one year’s use, 12.5 billion barrels.
400
12.5
=
32:
the
reserve
lasts
32
years
if
use
stays
the
same.
This is an example. Type your own values to start a new problem.
y (years)
=
Q (billion barrels)
÷
r (billion barrels a year)
Formulas
y
=
Q
r
32
=
400
12.5
Assumptions
•
The yearly use stays the same, and no new reserves are found.
•
Reserves are the amount that can be recovered at today’s prices with today’s technology.
•
Nonrenewable resources form over millions of years, far slower than they are used.
Step-by-step
WE KNOW
Q = 400 billion barrels, r = 12.5 billion barrels a year
FIND
years it lasts (y)
Step 1 · Find years it lasts (y)
Use y = Q ÷ r
How many years of use the reserve holds.
y
=
400
12.5
y
=
32
years
Check
Put the numbers back in. Both sides should match.
32
=
400
12.5
✓
Topic check
See what you know: 5 questions on this topic
New questions each time. Pass to mark it complete.
Refresh
Related lessons
Human impacts, resource management and engineering solutions
Main lesson
Where electricity comes from
Use this for “What share of US electricity comes from fossil fuels, and what share is renewable?”
How long a reserve lasts when use grows
Use this for “600 billion barrels are used at 15 billion a year, and use grows steadily by 2% a year. How many years will they last?”
How coal forms
Use this for “Describe how fossil fuels such as coal form.”