Question

Laura is baking a cake. The recipe says that she has to mix 64 grams of chocolate powder to the flour. Laura knows that 1 cup of that particular chocolate powder has a mass of 128 grams. She added two over three of a cup of chocolate powder to the flour. Should Laura add more chocolate powder to make the exact recipe, or did she go over and by what amount?

Answer 1

One cup of that particular chocolate powder has a mass of 128 grams: 1c = 128g

64 grams of chocolate powder is x cups.1c = 128gx = 64g
1c : 128 g = x : 64gx = 1c : 128 g * 64 gx = 0.5 c64 grams of chocolate powder is 0.5 cups = 1/2 cups
She added two over three of a cup of chocolate powder: 2/3 cups
She need to add 1/2 cups: 1/2 = 3/6 cupsShe added 2/3 cups: 2/3 = 4/6 cups
So she added 4/6 - 3/6 = 1/6 cups more.

Answer 2

Answer: Laura needs to ad 64 grams of the chocolate powder, and she knows that each cup of the chocolate powder has 128 grams.

The problem says that she added 2/3 of a cup of chocolate powder to the flour.

If one cup of the powder contains 128g, then 2/3 of a cup contains (2/3)*128g = 85.3g of chocolate powder.

Laura wanted to put 64 g of it, so she went over by (85.3g - 64g) = 21.3g.

You also can see the difference in cups:

if one cup is 128 grams and she wanted to use 64 grams, then she should used half a cup, this is 1/2 cup.

But she used 2/3 cups, then the difference is:

2/3 - 1/2 = 4/6 - 3/6 = 1/6.

So she used 1/6 of a cup more than she should.