Weight of the third rock = 16.76 grams
The first rock weighed 3.63 grams.
The second rock weighed 1.12 grams more than the first rock. When you hear ‘more than’, that means to add. Rock 2 = 3.63 grams + 1.12 grams = 4.75 grams
The third rock weighed twice as much as the total weight of the first two rocks. To get the ‘total’ weight of the first two rocks, add them together. 4.75 + 3.63 = 8.38 grams.
If the third rock weighed ‘twice as much’ that means it’s two times the weight of the first two rocks, that means you have to multiply 8.38 by two.
8.38 x 2 = 16.76 grams
