Solution

196230

Problem / game
Doubling Fives Back to problem
First name
Ru
School
Clifton Hill Primary School
School's Twitter handle
We have none
Country
Australia
Age
12

The answer to this is that it will make a muliple of 10 as 5 + 5 = 10 and 0 + 0 = 0 and then just add the 10s place together so it will just make something that ends with 0 and will make it a multiple of 10 and 5.