use cross multiplication. 42 inches is your 100%. your fraction would be 42/100
then, to find by what percent it has increased, since 47 is your new height, and you are trying to find the percentage for that, the fraction will be 47/X.
42 47
----- -----
100 X
(100 * 47) / 42 = X
100 multiplied by 47, then divided by 42, the result is X
your answer should be 111%. Subtract 100 from 111, to get the increased percent.
Answer: 11%
I did this last year, so it may be a little rusty. If im wrong, hopefully someone will correct me, if not, im pretty sure this looks rights. Your methods may also be different. i use cross mulitplication
