Ben's estimation strategy gives him an answer of 7 g of nickel in 35 g of the substance.
The exact answer is there is 7.7 g of nickel in 35 g of the substance.
Using a proportion for Ben's estimate, we set the first ratio as 0.2/1, since he states there are around 0.2 g of nickel in 1 g of the substance. The other ratio would be x/35, with x representing the amount of nickel and 35 being the amount of the substance:
0.2/1 = x/35
Cross multiply:
0.2*35 = 1*x
7 = x
Ben's estimate is 7.
There are 0.52 g of copper and 0.26 g of zinc in 1 g of the substance. This makes up 0.52+0.26 = 0.78 g out of 1 g total. To find the remaining amount (nickel), subtract from 1:
1 - 0.78 = 0.22
There are 0.22 g of nickel in 1 g of the substance.
This means there are 0.22*35 = 7.7 g of nickel in 35 g of the substance.
