Trevor's maths learning

I learnt how to skip count in 2's 5's 10's-


My question in teacher lesson was:
Roslyn has 15 chocolate bars. Trevor very kindly  gave her 10  more. how many
does she have altogether?

Because I knew Roslyn had 15 chocolate bars, and I gave her 10 more chocolate bars,  I skipped counted in 2's then i got 25.  


Children making groups of 5's to skip count:

 Teacher question:

 Teacher follow up activity: