Sum of digits
"What was lacking in the usual approach, even at its best, was any sense of genuine enquiry, or any stimulus to curiosity, or appeal to the imagination. There was little feeling that one can puzzle out an approach to fresh problems withouth having to be given detailed instructions."
- Aspects of Secondary Education, HMSO 1979
The number 12 is equal to exactly four times the sum of its digits. So is the number 24.
- Can you find a whole number which is equal to exactly twice the sum of it's digits? Is your answer the only possible answer?
- Can you find a whole number which is equal to exactly three times the sum of it's digits? Is your answer the only possible answer?
- Which numbers orther than 12 and 24 are equal to exactly four times the sum of their digits?
(MP pg 11)
