211. To obtain the product of two numbers 4.27 and 11.56 with an accuracy of 1, both factors are taken with one decimal place; what approximate values of the factors provide the smallest error in the product?
211. Generally, one factor should be taken with a deficiency, the other with an excess; here it is most appropriate to take $4.3 \times 11.5$ (why not the other way around?).