# Parse out 2/3 of 30 minus 11

Note - I am not a math teacher; I am seeking an answer from a math teacher.

While helping my son with his 5th grade homework today we had one answer wrong. I'm not sure I agree with the book and wanted to see if there's a rule on this. The assignment is to write the expression for the phrase.

The problem is 2/3 of 30 minus 11. You can read that two ways: "Two thirds of [pause] thirty minus eleven" "Two thirds of thirty [pause] minus eleven"

Our answer was (2/3 * 30) - 11 and we are aware the parenthesis do not matter here. This also fits with the fact that 30 is divisible by 3. The book's answer is 2/3 * (30 - 11).

Is there a specific reason for this? Misprint?

I'll add that the book lists the answer to 1/4 times 8 increased by 11 as being 1/4 * 8 + 11 which we have correct. Seems quite similar.

• Keep in mind order of operations. But I would interpret that as $2/3 \times 30 -11$. Mar 16 '15 at 19:08
• Since "of" is read in this context as signifying multiplication, I would agree that you have $2/3 \times 30 - 11$, which, using the order of operations, would be your answer (and not the book's!). Mar 16 '15 at 20:10
• I might add that as currently written, it is better suited for math.SE. But I think it is a good question if we adjust to how to word such problems in an education context. Mar 16 '15 at 20:39