is this view on inflation correct?

say inflation remains constant at 10%

that means your money is loosing 10% of its buying power per year

meaning if you save 10,000$ over 10 years; it would then only have the buying power of about 3,500?

(10,000 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9 x 0.9) = 3,486.78$

which also means youd need to invest in a decent index fund recieving 10% roi just to battle inflation and to have the same buying power that you had when you started saving