The multiple of 9 in 100 is 9, 18, 27, …, 99, *** 1 1, where 8 does not contain 9.
In 100, there are 9, 19, 29, …, 79, 89, 90, 9 1 99, 19 in * *.
In 100, there are 9,90,99, ***3 numbers containing multiples of 9 at the same time.
So the number 19-3= 16 contains 9 but is not a multiple of 9.
So clap your hands 8+ 16×2+3×4=52 (times).
A: At 100, the children applauded 52 times.