Junior high school math problem: the cost of developing a house in a real estate has increased with the price increase 10% ..............

Let the original cost be C and the original profit rate be R.

Then: the original price is C/( 1-r)

The original profit is c/(1-r)-c = RC/(1-r) (original price-original cost).

The current price is (1+0.5) c/(1-r) =1.5c/(1-r) (1.5 * original price).

The current cost is c (1+10%) =1.1c (1.1* original cost).

The current profit is1.5c/(1-r)-1.1c (current price-current cost).

So1.5c/(1-r)-1.1c = 1.6 * RC (1-r) (current profit =1.

0.5r=0.4

The solution is r=0.8 (that is, 80%)