[ Percentage and Ratio Problems ]

Joe knows that to convert from pounds to kilograms, you need to divide the weight in pounds by 2 and then decrease the resulting number by $10 \%$. From this, Joe concluded that to convert from kilograms to pounds, you need to multiply the weight in kilograms by 2 and then increase the resulting number by $10 \%$. By what percentage of the correct value of the weight in pounds will he be wrong?
According to the condition, 1 pound equals $0.5 - 0.05 = 0.45$ kg. When converting 0.45 kg to pounds using John's method, he will get $0.9 + 0.09 = 0.99$ pounds, which is $1\%$ less.

## Answer

By $1\%$ less.