For near double sums such as 8+7= __, the children are encouraged to use their double facts to answer. For example, for 8+7= the children should do 8+8=16 then -1 because it was 8+7.
Have fun!
http://www.transum.org/Maths/Activity/Beat_The_Clock/
Challenge:
The same can be done for multiplication and division if your child is confident to answer multiplication sums without a grid or manipulatives.