Errors with the programs were one problem, but errors caused by the computer were another. The computer frequently misread the binary digits it was given. The engineers thought the mathematicians could compensate for this by programming arithmetic checks, and the mathematicians would too readily assume that a wrong program result was due to a computer error when it was due to a program error. This caused inevitable friction between the mathematicians and the engineers. At the centre of this was a program that Woods had written for inverting a matrix to solve 40 simultaneous equations, which was a large number for the time. The long rows of data required by this calculation took the computer too long to process without an error. For one dispute Woods went to Tom Kilburn, who was second only to Professor Sir Frederic Calland Williams in the engineering department. Kilburn was polite but did not argue, and she felt he was ignoring her complaint. However, 50 years later when she asked him about the exchange, he said that he had not argued "because knew [she was right."