Learning Curve

Hiya I am working on a question that appeared in the 2014 specimen paper. Tech World is a company which manufactures mobile phone handsets. From its past experiences, Tech World has realised that whenever a new design engineer is employed, there is a learning curve with a 75% learning rate which exists for the first 15 jobs. A new design engineer has just completed his first job in five hours. Note: At the learning rate of 75%, the learning factor (b) is equal to –0·415. How long would it take the design engineer to complete the sixth job? My question is - for my answer I got 1.447 hours the answer is 1.442 hours how do we know about roundings? will roundings matter in a section C question if this was to appear? thanks