Q9 - Electricity use between 1973 and 1989

[nbayar1212]

I picked C but even when I was taking the test I wasn't sure why B is exactly wrong....

Can someone explain it with some kind of hypothetical?

[abcde]

Hello,

I think (B) is incorrect because the statement could be still valid even if the use of energy other than electrical energy has increased.

Here is the hypothetical example I came up with

Increased rate of the total energy - 8%
Increased rate of the electrical energy - 50%

In 1973:
Total Energy 100
Electrical Energy 10
Other than Electrical Energy 90

In 1989
Total Energy 108
Electrical Energy 15
Other than Electrical Energy 93

As you can see, other than electrical energy can be increased without violating any stimulus that was given to us.

I hope this makes sense!
Thank you.

[rinagoldfield]

Jiyeon’s explanation above about why B is incorrect is excellent. Awesome work, Jiyeon.

This is an inference question. The stimulus gives us three pieces of information to work with:

1. Total energy use increased by less than 10% between 1973 and 1989
2. Electrical energy use increased by more than 50% between 1973 and 1989
3. The GNP (the total value of goods and services produced in the nation) increased by more than 50% between 1973 and 1989

(C) gives a correct inference. If total energy use increased by less than 10% while electrical energy use increased by more than 50%, then the proportion of electrical energy use to total energy use must have increased as well.*

(A) incorrectly infers that more electrical energy was used in 1989 than any other kind of energy. What if electrical energy only constituted 1% of all energy used in 1973? Even after a 51% increase, only 1.51% of all energy used would be electrical. 1.51% is hardly "most."

(B) also makes an incorrect inference about the relationship between electrical energy and other kinds of energy. Jiyeon wrote a great hypothetical to disprove this answer choice above. Here’s another:

1973:
Total energy use: 100
Electrical energy use: 2
Non-electrical energy use: 98

1989
Total energy use (after a 9% increase): 109
Electrical energy use (after a 51% increase): 3.02
Non-electrical energy use: 105.98

In this example, non-electrical energy use increased rather than decreased. Throw out this answer choice.

(D) Again, we can’t infer anything how much electrical energy was used in relation to other kinds of energy. We also don’t know anything about the types of energy used to produce the GNP.

(E) talks about the electrical energy produced in 1973; we are concerned with energy use. Even if this answer choice discussed energy use, however, it would still be wrong: we don’t know anything about the relationship between energy use and the GNP.

In general: remember to be wary of making assumptions about absolute amounts when dealing with percents.

*Here’s a hypothetical scenario that demonstrates this:

1973
Total energy use: 100
Electrical energy use: 40

1989
Total energy use (after a 9% increase): 109
Electrical energy use (after a 51% increase): 60.4

The proportion of electrical energy use to total energy use is .4 in 1973; that same proportion is .55 in 1989.

[LauraS737]

If the stimulus said that total energy did not increase AND stayed the same, could (B) be correct?

[andrewgong01]

If the stimulus said that total energy did not increase AND stayed the same, could (B) be correct?

Yes because if the country is still using say 100 units of energy but now we learn that electrical energy use grew by 50% and assuming the total energy use grew by 10% is no longer valid, then some other energy source must have decrease. The total pie is the same; however, one slice of the pie is now bigger so another slice must be smaller in this zero-sum game case.