Question

Match the following equation to the correct situation.

30%(b - 18) = 30%b - 5.4
A.
Last month's electricity bill was 5.4 kW-h less than 30% of this month's bill.

B.
The number of songs available for download from 30% of b artists.

C.
The number of cups of coffee thrown away by 30% of b senators during 5.4 speeches.

D.
The amount of chili eaten from 30% of 5.4 less than b bowls.

Answer 1

A. Last month's electricity bill was 5.4 kW-h less than 30% of this month's bill.

Explanation:

The given expression is:

`30\%(b-18)=30\%b-5.4`

The above expression tells us that 30% is of the quantity 'b' and 5.4 is being subtracted from the result of the percentage.

Choice A:

If we consider the present month's bill as 'b'. Then 30% of present month's bill can be represented as 30% of b = 30%b.

Now, if the previous month's bill is 5.4 kW-h less than 30% of this month's bill, then this statement can be represented as:

Previous bill = 30% of Current bill - 5.4 =
`30\%b-5.4`

Hence, choice A justifies the given expression.

Choice B:

The expression for choice B could be number of songs available for download from 30% of 'b' artists is
`30%b`.

Choice C:

5.4 speeches doesn't make any sense.

Choice D:

5.4 less than 'b' bowls mean
`b-5.4`. Now, 30% of this is
`30%(b-5.4)=30%b-30%(5.4)`.

This is also not the correct expression.

Therefore, only choice A is the correct justification of the given expression.