It may seem unbelievable, but government employees in China during the T'ang Dynasty (618-906 A.D.) had to take tests roughly equivalent to our present-day civil service examinations. The standard test for the arithmetic portion of the examination was prepared by the great Chinese Mathematician Hsia-Hou Yang. Here is one of the questions. Could you have passed this part of the government examination ?

" A farmer owned 18 k'o, 7 t'ow, 5 ho of rough and unprocessed rice. [Note: A k'o, approximately equal to one bushel, was the equivalent of 10 t'ow or 100 ho.] The farmer took his rice to the miller to be exchanged for processed and milled rice at the rate of 1 k'o, 6 t'ow of processed rice for each 3 k'o of rough rice. How much processed rice did the farmer receive?"

Solution to the Problem:

To simplify the computation, convert all units to ho.
The desired amount of rice = 1,875 / 300 x 160 = 1,000 ho, which is equivalent to 10 k'o.
You can set up a proportion:
1875 / x = 300 / 160
Solving for x, you get x = 1,000 ho.