1- increase 1000 dollars by 10% then decrrese ur answer by 10% wat do u notice?

Question

2- my parents increased my pocket money by 10% then 3 months later increased it by further. 10%'. My father said there was an increase of 21% , can u explain this?

Answer 1

increasing something by 10% is the same as multiplying it by 1.1
decreasing something by 10% is the same as multiplyig it by .9
( 1 - .1 = .9)

so $1000( 1.1)(.9) = 990

2. (see above argument)

suppose your money is x
first increase = 1.1x
second increase = (1.1x)(1.1) = 1.21x
which is a 21% increase
(your dad knows his math)