Countdown’s Rachel Riley, who has been the show’s maths genius for 14 years, was left red faced in the latest episode when she was unable to solve the mathematical problem.The contestants on Wednesday's episode were challenged to use the numbers selected to create the final number of 477, which none of the contestants were able to do. Where Rachel, 37, would normally impress viewers and reveal how to reach the exact number in no time, on this occasion she was unable to do so and told the show's host, Colin Murray, “You will have to come back to me Colin." Viewers quickly picked up on Rachel's blunder with fans claiming the sum was “obvious”.