The difference between grandpa and Xiaoming this year is 70- 10=60 (years old).
No matter how many years, grandpa and Xiaoming are 60 years apart.
Grandpa is five times older than Xiaoming, that is, grandpa is five-1= four times older than Xiaoming.
So Xiao Ming's age was 60 ÷ 4 = 15 (years old).
15- 10=5 (year)
Five years later, grandpa is five times as old as Xiaoming.