there are many examples

 one for  introducing  subtraction  ( you may visit online on www.scertharyana.gov.in the  7th lesson of class1 maths text  book of Haryana Govt. schools)

 Make two groups. Take 7 marbles  and  display them on a table. Count in front of all.

Call two students  A and B ( one from each group)

 Student A will hide some marbles out of those  in his fist without showing to  student B and B will try to tell or guess number of marbles in fist. If answer is not correct then let them play again and again.

( Teacher will not give hint or  tell the answer or points to count  remaining marbles. Students will try and play this for two or more days )

You may reduce the challenge by taking total marbles  4 instead of 7. But do not tell the answer or give hint.