V-3 If we append a zero to the right of a number, then divide the resulting number by 15, then append 3 to the right of the resulting quotient, and divide the thus obtained number by 13, we will get 11. What is that number?
Solution. If we multiply 11 and 13, we get 143. If we remove the digit 3 from the number 143, we get the number 14. If we multiply 14 by 15, we get 210. If we remove the zero from 210, we get the number 21. This is the desired number.