Solution

Forwards Add Backwards Xuchen

Problem / game
Forwards Add Backwards Back to problem
First name
Xuchen
School
LML
Country
Luxembourg
Age
12
File
NRich forwards add backwards .pdf

Imagine the 3 digit number is ABC. Then for example you use 700-800 as an example. Numbers to add up to 7 can be 6, 1, 5 and 2. You can do 6+1=7 times 101 which is 707. Then you do 0 times 20 which is 0. So the answer is 707. I then just realized all the even numbers in the middle can be part of it. So: 707, 727, 747, 767, 787.