SME
Grade 12 Science · Problem type
Where electricity comes from
Use this for “What share of US electricity comes from fossil fuels, and what share is renewable?”
Chart
Fossil fuels: 59%
Renewable: wind, water and sun: 20%
This is an example. Type your own values to start a new problem.
g
Natural gas
example · %
n
Nuclear
example · %
k
Coal
example · %
w
Wind
example · %
h
Hydroelectric
example · %
s
Solar
example · %
o
Other sources
worked out (not typed) · %
F
Fossil fuels
worked out (not typed) · %
R
Renewable: wind, water and sun
worked out (not typed) · %
Formulas
F
=
g
+
k
59 = 43 + 16
R
=
w
+
h
+
s
20 = 10 + 6 + 4
o
=
100
−
F
−
n
−
R
2 = 100 − 59 − 19 − 20
Assumptions
•
Shares of US electricity in about 2023, rounded.
•
Oil makes almost no electricity; it fuels transport.
•
Biomass and geothermal are in other.
Step-by-step
WE KNOW
g = 43%, n = 19%, k = 16%, w = 10%, h = 6%, s = 4%
FIND
fossil fuels (F), renewable: wind, water and sun (R), other sources (o)
Step 1 · Find fossil fuels (F)
Use F = g + k
Add up the fossil shares.
F
=
43
+
16
F
=
59%
Step 2 · Find renewable: wind, water and sun (R)
Use R = w + h + s
Add up the renewable shares.
R
=
10
+
6
+
4
R
=
20%
Step 3 · Find other sources (o)
Use o = 100 − F − n − R
Whatever is not fossil, nuclear or wind, water and sun is other.
o
=
100
−
59
−
19
−
20
o
=
2%
Check
Put the numbers back in. Both sides should match.
59 = 43 + 16 ✓
20 = 10 + 6 + 4 ✓
2 = 100 − 59 − 19 − 20 ✓
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