Erin raised her hand feeling a little worried if her answer would be right. She'd met with Professor Hadley before, but the classroom is different. She smiled at her and started at once, "I think, we need to add up numbers 4 and 7, Professor. We are provided with the designated meaning of numbers 0 through 9 and so to come up with 1 single digit, we need to add two or more digits on and on until we get one single unified digit. The meaning of 47 would be that of number 2. We add 47 together and we get 11. We add the digits again and we get 2."