If a recipe calls for 1 lb. 4 oz. of sugar and the chef makes half of the recipe, how much sugar is needed?

To determine how much sugar is needed when halving the recipe, you start by converting the total amount of sugar from pounds and ounces to ounces only.

In this case, 1 pound is equal to 16 ounces. Therefore, 1 lb. 4 oz. can be converted to ounces as follows:

1 lb. = 16 oz.

Adding the additional 4 oz. gives you:

16 oz. + 4 oz. = 20 oz. of sugar in total.

Now, to find out how much sugar is needed for half of the recipe, you simply divide the total number of ounces by 2:

20 oz. ÷ 2 = 10 oz.

Thus, when the recipe is halved, 10 ounces of sugar are needed. This matches the correct choice provided in the question.