[AnimalMuppet]

I still don't think that's right.

You have food and fuel, which is some fraction of the economy - call that F. You have a rate of inflation in fuel and food - call that f. And you have a rate of inflation in everything else - call that e. Then you have

  3.8 = e(1-F) + fF.

You also have e = 2.8.

I think what you're claiming is that fF = 1.0, so that e(1-F) = 2.8. And I think that's wrong. When they say inflation apart from food and fuel is 2.8, they mean e, not e(1-F).

[giantg2]

You're over complicating it because you don't need rates within subcategories when looking at the whole - e is given and f is useless.

3.8 - 2.8 = 1

The overall inflation is 3.8. Overall inflation without food and fuel is 2.8. The overall inflation attributable to food and fuel must then be 1 (this is different than rste of inflation within food and fuel as a category, f).