Answer:
Step-by-step explanation:
ahh that's like a math tongue twister :P
so just remember that when you are given the final amount, as the 0.99 is, then you want to divide by the total, like this
0.99 / 9.90 =
we don't really need a calculator for this, b/c you can see that the answer will come out to a one, but, where is the decimal, huh
my calculator put the decimal here 0.1
so that's 10% right? which totally makes sense.. right? 0.99 is 10% of 9.90... just move the decimal one place in the 9.9 to get .99 see? so that kinda helps us know where the decimal goes in the answer, if that make sense? The decimal gets moved one place to the LEFT of the one, in our answer when we just did the math in our head.
anyway.. leave a comment if you have more questions :)